CN110808568A - Method and protection device for preventing protection misoperation caused by direct-current voltage offset - Google Patents
Method and protection device for preventing protection misoperation caused by direct-current voltage offset Download PDFInfo
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- CN110808568A CN110808568A CN201911152211.6A CN201911152211A CN110808568A CN 110808568 A CN110808568 A CN 110808568A CN 201911152211 A CN201911152211 A CN 201911152211A CN 110808568 A CN110808568 A CN 110808568A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
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Abstract
The invention discloses a method and a protection device for preventing protection maloperation caused by DC voltage offset, comprising the following steps: step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay; step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, performing step S3, and if the fault detected firstly is the direct-current voltage offset fault, performing step S4; step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state; in step S4, the protection device starts the dc offset blocking outlet loop, and the dc offset blocking module in the protection outlet loop is in a disconnected state. By implementing the invention, the problem of protection misoperation caused by DC voltage offset is solved; when direct-current voltage deviation and grid short-circuit fault occur successively, the tripping outlet is protected from being influenced by a locking loop completely.
Description
Technical Field
The invention belongs to the field of relay protection, and relates to a method and a protection device for preventing protection misoperation caused by direct-current voltage offset.
Background
The direct current system of the transformer substation provides a direct current power supply for devices such as protection, spare power automatic switching, stable control and measurement and control, and is one of the most important public equipment. Both direct current grounding and direct current parasitics can cause direct current voltage offset, possibly cause protection misoperation, and are major potential safety hazards resulting in power failure accidents.
Direct-current grounding and direct-current parasitic defects frequently occur, and statistics data of a power grid in a certain large area in nearly three years show that the two types of defects account for 13% of the defects of the whole secondary circuit. In particular, dc voltage offsets caused by dc grounds and dc parasitics have resulted in numerous power outage accidents. Therefore, it is of great importance to develop a method for preventing the dc voltage offset from causing the protection malfunction.
In terms of dc grounding, some scholars propose measures for preventing dc grounding from the operation and maintenance perspective, but cannot prevent the measures from causing protection maloperation. Some researchers have designed a dc insulation monitoring system. The system can prevent protection misoperation caused by one-point direct current grounding, but parameters such as direct current system capacitance, insulation resistance, tripping coil internal resistance and the like need to be input. The accurate measurement of these parameters is extremely difficult, so the method is difficult to be popularized and applied. In the aspect of direct current parasitic, no literature exists for analyzing the principle of protection maloperation caused by direct current parasitic and a method for solving the problem of maloperation prevention; therefore, there is no method for preventing the dc voltage offset from causing the protection malfunction.
During the operation of the power grid, a plurality of factors can cause direct current grounding, which is summarized as follows:
(1) the service life is long, and the insulation is reduced due to the aging of the cable; (2) water enters a junction box of the meter, so that the insulation of a cable in the meter is reduced due to corrosion; (3) in the process of acceptance, the cables which are not detected in the pressure test are stripped or crushed; (4) small animals such as mice bite and damage the cable skin; (5) when the protection screen is removed, the cable is disconnected at one end only. The end of the disconnection is not covered by an insulating tape and touches the ground; (6) the direct current arrester is broken down; therefore, during grid operation, dc ground faults often occur.
The direct current parasitic causes are various, such as design defects, wiring errors, insulation reduction between nodes in the instrument, poor insulation of the small detection bus of the storage battery, and the like. Dc parasitics also occur from time to time in grid operation.
Dc parasitics are undesirable associations that arise between two independent secondary loops. Compared with direct current grounding, the probability of protection misoperation caused by the transient process is extremely low. Moreover, no document reports the protection malfunction caused by the dc parasitic transient process.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a method and a protection device for preventing protection malfunction caused by dc voltage offset, so as to solve the problem of a major potential safety hazard of a power failure accident caused by protection malfunction caused by dc voltage offset.
The invention provides a method for preventing protection misoperation caused by direct-current voltage offset, which comprises the following steps:
step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay;
step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, then step S3 is carried out, and if the fault detected firstly is the direct-current voltage offset fault, then step S4 is carried out;
step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state;
in step S4, the protection device starts the dc offset blocking outlet loop, and the dc offset blocking module in the protection outlet loop is in a disconnected state.
Further, in step S1, the monitoring of the operation condition of the primary device is to determine whether the primary device fails through voltage and current sampling, and the specific determination process is to determine that the primary device fails if the protection action relay TJ is in an excitation state, that is, the normally open node of the protection action relay TJ is closed; and if the protective action relay TJ is in a field loss state, namely a normally open node of the protective action relay is disconnected, judging that the primary equipment normally operates.
Further, in step S1, the monitoring of the dc voltage offset of the outlet relay is to collect the dc voltage value U across the outlet relay TQTQ+、|UTQ-And making a logical judgment on the | s.
Further, in step S1, when the dc voltage across the two terminals of the outlet relay TQ collected by the protection device satisfies one of the following three conditions, it is determined that the dc voltage is shifted, and the dc voltage shift locking circuit is started:
negative terminal voltage | U of outlet relayTQ-I is more than 1.1 times of action value U of outlet relayTI.e. UTQ-|＞110％UTThen, set the first DC offset latching start relay Xq1Excitation;
negative terminal voltage | U of outlet relayTQ-Less than 0.1 times DC power supply voltage UdI.e. UTQ-|<10％UdThen set a second DC offset latching start relay Xq2Excitation;
the voltage difference value of two ends of the outlet relay is more than 0.5 time of the DC power supply voltage UdI.e. UTQ+-UTQ-|＞50％UdThen, a third DC offset latching start relay X is setq3And (6) excitation.
Further, in step S2, the protection outlet circuit includes a protection action relay, and when the primary device fails, the protection action relay is excited and de-excited by the fixed delay.
Further, in step S2, the protection outlet loop includes a dc voltage offset blocking module, where the dc voltage offset blocking module is formed by connecting a normally closed node of the BS, a normally open node of the TJ, and a normally open node of TBJ in parallel, and when a primary device fails, the normally open node of the TJ or TBJ is always in a closed state, so as to short-circuit the normally closed node of the BS.
On the other hand, the embodiment of the invention also discloses a protection device for preventing protection misoperation caused by direct-current voltage offset, which is used for realizing the following method:
step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay;
step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, then step S3 is carried out, and if the fault detected firstly is the direct-current voltage offset fault, then step S4 is carried out;
step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state;
step S4, the protection device starts a direct current offset locking outlet loop, and a direct current offset locking module in the protection outlet loop is in a disconnected state;
further, the apparatus comprises:
the protection outlet loop comprises a protection action relay TJ, an outlet relay TQ and a direct-current voltage offset locking module which are sequentially connected, and is used for protecting an outlet process from being influenced by direct-current offset during the period from the fault occurrence moment to the fault removal of the protection outlet and protecting a quick outlet to isolate the fault;
the direct current offset locking outlet loop is used for ensuring that when primary equipment does not have faults, the direct current offset protection does not malfunction, or ensuring that a protection device can normally remove the faults at an outlet during the direct current offset.
Further, the protection outlet circuit specifically includes:
the protective action relay TJ is excited when primary equipment fails, and is demagnetized through fixed time delay;
the outlet relay TQ is used for determining whether the direct-current voltage deviates or not according to the voltage change of the two ends of the outlet relay TQ;
the direct-current voltage deviation locking module is used for enabling direct-current voltage deviation to occur before and during primary equipment failure, protecting outlet loops to be always in a conducting state and not affected by the direct-current voltage deviation, and the direct-current voltage deviation locking module is formed by connecting a normally closed node of a direct-current voltage deviation locking relay BS, a normally open node of a protection action relay TJ and a normally open node of a tripping holding relay TBJ in parallel.
Further, in step S2, the dc voltage offset locking module specifically includes:
a trip hold relay TBJ for determining whether the primary equipment is in a fault condition;
the direct-current voltage deviation latching relay BS is used for disconnecting a protection outlet loop to prevent protection misoperation under the condition that direct-current grounding or direct-current parasitism occurs and primary equipment has no fault;
and a protective action relay TJ for performing excitation when the primary equipment fails.
Further, the dc offset blocking outlet loop specifically includes:
and the positive voltage U of the DC power supply of the protection deviced+Connected unit voltage type relay X1Double-position voltage type relay X2And unit voltage type relay X3Said unit voltage type relay X1Double-position voltage type relay X2Unit voltage relay X3The other end of the protective action relay TJ is connected with one end of a trip holding relay TBJ, a direct current voltage deviation locking relay BS and a protection device direct current power supply negative electrode voltage U in parallel, and the other end of the protective action relay TJ is connected with a trip holding relay TBJ, the direct current voltage deviation locking relay BS and the protection device direct current power supply negative electrode voltage U in sequenced-Protection device DC power supply negative pole voltage Ud-The DC offset locking module is also connected;
and the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq1Said DC offset latching start relay Xq1The other end is connected with a single-position voltage type relay X in sequence1DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq3Said DC offset latching start relay Xq3The other end is connected with a single-position voltage type relay X in sequence3DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq2Said DC offset latching start relay Xq2The other end is connected with a double-position voltage type relay X in sequence2DC power supply negative electrode voltage U of protection deviced-；
The protection device is used for protecting the positive voltage U of the direct-current power supplyd+And the protection action relay TJ in the protection outlet loop is also connected.
The embodiment of the invention has the following beneficial effects:
the embodiment of the invention provides a method and a protection device for preventing protection misoperation caused by direct-current voltage offset, wherein a direct-current offset locking outlet loop is newly added to the protection device and a direct-current offset locking module is newly added to an original protection outlet loop on the basis of voltages at two ends of an outlet relay TQ, so that the problem of protection misoperation caused by direct-current voltage offset is solved; when direct-current voltage deviation and power grid short-circuit faults occur successively, the tripping outlet is ensured to be protected from being influenced by a locking loop;
when the protection device detects that primary equipment fails, the protection device starts a protection outlet loop, and if direct-current voltages at two ends of an outlet relay TQ deviate due to direct-current grounding or parasitic during the period from the time of the failure to the time of removing the failure from a protection outlet, a direct-current deviation locking module is always in a conducting state, namely the outlet process is protected from being influenced by direct-current deviation, and a quick outlet is protected to isolate the failure; if the protection device detects that the direct-current voltage deviation of the outlet relay TQ occurs, the protection device starts a direct-current deviation locking outlet loop; during the period from the moment when the direct current offset occurs to the time when the direct current voltage recovers to normal, if the fault of primary equipment is not detected all the time, the direct current offset locking module is always in a disconnected state, namely the direct current offset protection is ensured not to be operated mistakenly; on the contrary, if the primary equipment is detected to have a fault, the direct current offset locking module is instantly switched to be in a conducting state, and the direct current offset locking module is not restored to be in a disconnecting state until the protection outlet is cut off from the fault, so that the protection device can be ensured to normally cut off the fault during the direct current offset period.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a main flow diagram of an embodiment of a method for preventing a protection malfunction caused by a dc voltage offset according to the present invention.
Fig. 2 is a schematic structural diagram of an embodiment of the protection device for preventing protection malfunction caused by dc voltage offset according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, which is a main flow diagram illustrating an embodiment of a method for preventing a protection malfunction caused by a dc voltage offset according to the present invention, in this embodiment, the method includes the following steps:
step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay;
in a specific embodiment, the monitoring of the operation condition of the primary equipment is to determine whether the primary equipment fails through voltage and current sampling, and the specific determination process is to determine that the primary equipment fails if the protective action relay TJ is in an excitation state, that is, a normally open node of the protective action relay TJ is closed; if the protective action relay TJ is in a field loss state, namely a normally open node of the protective action relay is disconnected, judging that the primary equipment normally operates;
specifically, the starting voltage of the outlet relay TQ is 50% -70% of the rated direct-current voltage, the criterion of the detection method in the embodiment of the invention is selected near the range, and the monitoring of the direct-current voltage deviation condition of the outlet relay is to acquire the direct-current voltage value U at the two ends of the outlet relay TQTQ+、|UTQ-I, carrying out logic judgment on the I;
outlet relay TQ negative terminal voltage | UTQ-Normal voltage of |, is between 0.4 and 0.6 times of DC power supply voltage UdIn between, i.e. 40% Ud<|UTQ-|<60％Ud；XfLatching the return relay for DC offset when 40% Ud<|UTQ-|<60％UdWhen the condition is satisfied, XfExcitation;
more specifically, when the dc voltage at the two ends of the outlet relay TQ collected by the protection device satisfies one of the following three conditions, it is determined that the dc voltage is deviated, and the dc voltage deviation locking loop is started:
negative terminal voltage | U of outlet relayTQ-I is more than 1.1 times of action value U of outlet relayTI.e. UTQ-|＞110％UTThen, set the first DC offset latching start relay Xq1Excitation;
negative terminal voltage | U of outlet relayTQ-Less than 0.1 times DC power supply voltage UdI.e. UTQ-|<10％UdThen set a second DC offset latching start relay Xq2Excitation;
the voltage difference value of two ends of the outlet relay is more than 0.5 time of the DC power supply voltage UdI.e. UTQ+-UTQ-|＞50％UdThen, a third DC offset latching start relay X is setq3And (6) excitation.
Step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, performing step S3, and if the fault detected firstly is the direct-current voltage offset fault, performing step S4;
in a specific embodiment, the protection outlet loop comprises a protection action relay TJ, when primary equipment fails, the protection action relay TJ is excited, and the protection action relay TJ is demagnetized through fixed time delay;
specifically, the protection outlet circuit comprises a direct current voltage offset locking module, the direct current voltage offset locking module is formed by connecting a normally closed node of a direct current voltage offset locking relay BS, a normally open node of a protection action relay TJ and a normally open node of a trip holding relay TBJ in parallel, when primary equipment breaks down, the normally open node of the protection action relay TJ or the trip holding relay TBJ is necessarily in a closed state, and therefore the normally closed node of the short circuit direct current voltage offset locking relay BS is short-circuited, and therefore, the protection outlet circuit is always in a conducting state and is not influenced by direct current voltage offset regardless of the fact that the direct current voltage offset occurs before the primary equipment breaks down or in the fault.
Step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state;
in step S4, the protection device starts the dc offset blocking outlet loop, and the dc offset blocking module in the protection outlet loop is in a disconnected state.
As shown in fig. 2, on the other hand, the embodiment of the present invention further provides a protection device for preventing a protection malfunction caused by a dc voltage offset, so as to implement the following method:
step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay;
step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, performing step S3, and if the fault detected firstly is the direct-current voltage offset fault, performing step S4;
step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state;
step S4, the protection device starts a direct current offset locking outlet loop, and a direct current offset locking module in the protection outlet loop is in a disconnected state;
specifically, the device includes:
the protection outlet loop comprises a protection action relay TJ, an outlet relay TQ and a direct-current voltage offset locking module which are sequentially connected, and is used for protecting an outlet process from being influenced by direct-current offset during the period from the fault occurrence moment to the fault removal of the protection outlet and protecting a quick outlet to isolate the fault;
in a specific embodiment, the protection outlet circuit specifically includes:
the protective action relay TJ is excited when primary equipment fails, and is demagnetized through fixed time delay;
the outlet relay TQ is used for determining whether the direct-current voltage deviates or not according to the voltage change of the two ends of the outlet relay TQ;
the direct-current voltage offset locking module is used for protecting the outlet loops from being influenced by the direct-current voltage offset when the direct-current voltage offset occurs before and during the primary equipment failure;
specifically, the dc voltage offset locking module specifically includes:
the trip holding relay TBJ is used for judging whether the primary equipment is in a fault state, when the primary equipment has a fault, the primary equipment is isolated from the excitation of the protection action relay, the trip holding relay TBJ is always in an excitation state, and the other moments are in a field loss state, namely the trip holding relay TBJ can be used for judging whether the primary equipment is in the fault state;
the direct-current voltage offset latching relay BS is used for disconnecting a protection outlet loop to prevent protection misoperation under the conditions of direct-current grounding or direct-current parasitism and no fault of primary equipment, belongs to a unit voltage type relay, and is excited under the condition that the voltage at two ends of the relay is more than 0.5 time of the direct-current power supply voltage;
and a protective action relay TJ for performing excitation when the primary equipment fails.
The direct current offset locking outlet loop is used for ensuring that the direct current offset protection does not malfunction when primary equipment does not have a fault, or ensuring that a protection device can normally remove the fault at an outlet during the direct current offset;
in a specific embodiment, the dc offset blocking outlet loop specifically includes:
and the positive voltage U of the DC power supply of the protection deviced+Connected unit voltage type relay X1Double-position voltage type relay X2And unit voltage type relay X3Said unit voltage type relay X1Double-position voltage type relay X2Unit voltage relay X3The other end of the protective action relay TJ is connected with one end of a trip holding relay TBJ, a direct current voltage deviation locking relay BS and a protection device direct current power supply negative electrode voltage U in parallel, and the other end of the protective action relay TJ is connected with a trip holding relay TBJ, the direct current voltage deviation locking relay BS and the protection device direct current power supply negative electrode voltage U in sequenced-Protection device DC power supply negative pole voltage Ud-The DC offset locking module is also connected;
specifically, X1The excitation condition is that the voltage at two ends of the excitation is more than 0.5 time of the voltage of the direct current power supply; when X is presentq1When excited, its normally open node is closed, X1Excited by conduction of the circuit in which it is located, X1The protection device is used for preventing protection misoperation caused by a direct current one-point grounding transient process;
specifically, X3The excitation condition is that the voltage at two ends of the excitation is more than 0.5 time of the voltage of the direct current power supply; when X is presentq3When excited, its normally open node is closed, X3Excited by conduction of the circuit in which it is located, X3The protection device is used for preventing protection maloperation caused by direct current parasitism;
specifically, X2The excitation condition and the demagnetization condition are both the voltage at two ends of the direct current power supply which is more than 0.5 time of the voltage at two ends of the direct current power supply; when X is presentq2Upon excitation, Xq2Normally open node closed, X2The excitation circuit is conducted to excite; when X is presentfUpon excitation, XfNormally open node closed, X2Lost magnetism due to conduction of the lost magnetism loop, X2The protection device is used for preventing protection maloperation caused by direct current two-point grounding.
And the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq1Said DC offset latching start relay Xq1The other end is connected with a single-position voltage type relay X in sequence1DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq3Said DC offset latching start relay Xq3The other end is connected with a single-position voltage type relay X in sequence3DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Respectively connected DC offset latching start relay Xq2DC offset latching return relay XfSaid DC offset latching start relay Xq2Latching return relay X with DC offsetfParallel connection and two-position voltage type relay X connected with the other end in sequence2DC power supply negative electrode voltage U of protection deviced-；
The protection device is used for protecting the positive voltage U of the direct-current power supplyd+And the protection action relay TJ in the protection outlet loop is also connected.
In a specific embodiment, when a dc voltage offset occurs, the operation of the locked outlet loop is as follows:
Xq1、Xq3、Xq2at least one of the three DC offset latching start relays is excited.
X1、X2、X3At least one of the three relays is excited, and at least one of the corresponding normally open nodes is closed.
If the period from the time when the DC voltage deviation occurs to the time when the DC voltage recovers to normal, the primary equipment has no fault, namely the normally closed nodes of TJ and TBJ are in a closed state, because of X1、X2、X3The normally open nodes are in parallel connection, and the BS can be excited as long as one normally open node is closed; the normally closed node of the BS is disconnected, so that the protection outlet loop is disconnected, and the protection misoperation prevention function is achieved.
If the primary equipment fails from the moment of occurrence of the DC voltage deviation to the period of recovery of the DC voltage, the normally closed nodes of the TJ and the T TBJ become an open state, the BS cannot be excited, and the normally closed node of the BS becomes a closed state, so that the fault of the protection outlet isolation is not influenced.
When the DC voltage returns to normal, X1、X2、X3And the normally closed node of the BS becomes closed, so that the isolation fault of the protection outlet is not influenced.
For further details, reference may be made to the preceding description of the drawings, which are not described in detail herein.
The embodiment of the invention has the following beneficial effects:
the embodiment of the invention provides a method and a protection device for preventing protection misoperation caused by direct-current voltage offset, wherein a direct-current offset locking outlet loop is newly added to the protection device and a direct-current offset locking module is newly added to an original protection outlet loop on the basis of voltages at two ends of an outlet relay TQ, so that the problem of protection misoperation caused by direct-current voltage offset is solved; when direct-current voltage deviation and power grid short-circuit faults occur successively, the tripping outlet is ensured to be protected from being influenced by a locking loop;
when the protection device detects that primary equipment fails, the protection device starts a protection outlet loop, and if direct-current voltages at two ends of an outlet relay TQ deviate due to direct-current grounding or parasitic during the period from the time of the failure to the time of removing the failure from a protection outlet, a direct-current deviation locking module is always in a conducting state, namely the outlet process is protected from being influenced by direct-current deviation, and a quick outlet is protected to isolate the failure; if the protection device detects that the direct-current voltage deviation of the outlet relay TQ occurs, the protection device starts a direct-current deviation locking outlet loop; during the period from the moment when the direct current offset occurs to the time when the direct current voltage recovers to normal, if the fault of primary equipment is not detected all the time, the direct current offset locking module is always in a disconnected state, namely the direct current offset protection is ensured not to be operated mistakenly; on the contrary, if the primary equipment is detected to have a fault, the direct current offset locking module is instantly switched to be in a conducting state, and the direct current offset locking module is not restored to be in a disconnecting state until the protection outlet is cut off from the fault, so that the protection device can be ensured to normally cut off the fault during the direct current offset period.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (10)
1. A method for preventing protection glitches caused by dc voltage offsets, comprising the steps of:
step S1, the protection device monitors the operation condition of the primary equipment and the DC voltage deviation condition of the outlet relay;
step S2, judging the sequence of primary equipment fault and direct-current voltage offset fault detected by the protection device, if the fault detected firstly is the primary equipment fault, performing step S3, and if the fault detected firstly is the direct-current voltage offset fault, performing step S4;
step S3, the protection device starts a protection outlet loop, and a direct current locking module in the loop is always in a conducting state;
in step S4, the protection device starts the dc offset blocking outlet loop, and the dc offset blocking module in the protection outlet loop is in a disconnected state.
2. The method according to claim 1, wherein in step S1, the monitoring of the operation condition of the primary device is to determine whether the primary device has a fault by sampling voltage and current, and the specific determination process is to determine that the primary device has a fault if the protective action relay TJ is in an excited state, i.e. its normally open node is closed; and if the protective action relay TJ is in a field loss state, namely a normally open node of the protective action relay is disconnected, judging that the primary equipment normally operates.
3. The method as claimed in claim 2, wherein in step S1, the monitoring of the dc voltage offset of the outlet relay is to acquire the value U of the dc voltage across the outlet relay TQTQ+、|UTQ-And making a logical judgment on the | s.
4. The method as claimed in claim 3, wherein in step S1, when the dc voltage across the outlet relay TQ collected by the protection device satisfies one of the following three conditions, it is determined that the dc voltage is shifted, and the dc voltage shift lock loop is started:
outlet relay TQ negative terminal voltage | UTQ-I is more than 1.1 times of action value U of outlet relayTI.e. UTQ-|＞110％UTThen, set the first DC offset latching start relay Xq1Excitation;
outlet relay TQ negative terminal voltage | UTQ-Less than 0.1 times DC power supply voltage UdI.e. UTQ-|<10％UdThen set a second DC offset latching start relay Xq2Excitation;
the voltage difference value of two ends of the outlet relay TQ is more than 0.5 time of the DC power supply voltage UdI.e. UTQ+-UTQ-|＞50％UdThen, thenSetting a third DC offset latching start relay Xq3And (6) excitation.
5. The method according to claim 4, characterized in that in step S2, the protection outlet loop comprises a protection action relay TJ, which is excited when a primary equipment fails, and is de-excited via a fixed time delay.
6. The method as claimed in claim 5, wherein in step S2, the protection outlet loop comprises a DC voltage offset blocking module, the DC voltage offset blocking module is composed of a DC voltage offset blocking relay BS normally closed node, a protection action relay TJ normally open node, and a trip hold relay TBJ normally open node in parallel, when a primary equipment fault occurs, the protection action relay TJ or the trip hold relay TBJ normally open node must be in a closed state, thereby shorting the DC voltage offset blocking relay BS normally closed node.
7. A protection device for preventing protection malfunction caused by DC voltage offset, which is used to realize the method of claims 1 to 6, and is characterized in that the device comprises:
the protection outlet loop comprises a protection action relay TJ, an outlet relay TQ and a direct-current voltage offset locking module which are sequentially connected, and is used for protecting an outlet process from being influenced by direct-current offset during the period from the fault occurrence moment to the fault removal of the protection outlet and protecting a quick outlet to isolate the fault;
the direct current offset locking outlet loop is used for ensuring that when primary equipment does not have faults, the direct current offset protection does not malfunction, or ensuring that a protection device can normally remove the faults at an outlet during the direct current offset.
8. The device according to claim 7, characterized in that said protection outlet circuit comprises in particular:
the protective action relay TJ is excited when primary equipment fails, and is demagnetized through fixed time delay;
the outlet relay TQ is used for determining whether the direct-current voltage deviates or not according to the voltage change of the two ends of the outlet relay TQ;
and the direct-current voltage offset locking module is used for protecting the outlet loops from being influenced by the direct-current voltage offset when the direct-current voltage offset occurs before and in the primary equipment fault all the time, and the outlet loops are always in a conducting state.
9. The apparatus of claim 8, wherein the dc voltage offset blocking module specifically comprises:
a trip hold relay TBJ for determining whether the primary equipment is in a fault condition;
the direct-current voltage deviation latching relay BS is used for disconnecting a protection outlet loop to prevent protection misoperation under the condition that direct-current grounding or direct-current parasitism occurs and primary equipment has no fault;
and a protective action relay TJ for performing excitation when the primary equipment fails.
10. The apparatus of claim 9, wherein the dc-offset locked outlet loop specifically comprises:
and the positive voltage U of the DC power supply of the protection deviced+Connected unit voltage type relay X1Double-position voltage type relay X2And unit voltage type relay X3Said unit voltage type relay X1Double-position voltage type relay X2Unit voltage relay X3The other end of the protective action relay TJ is connected with one end of a trip holding relay TBJ, a direct current voltage deviation locking relay BS and a protection device direct current power supply negative electrode voltage U in parallel, and the other end of the protective action relay TJ is connected with a trip holding relay TBJ, the direct current voltage deviation locking relay BS and the protection device direct current power supply negative electrode voltage U in sequenced-Protection device DC power supply negative pole voltage Ud-The DC offset locking module is also connected;
and the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq1Said DC offset latching start relay Xq1The other end is connected with a single-position voltage type relay X in sequence1DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Connected DC offset latching start relay Xq3Said DC offset latching start relay Xq3The other end is connected with a single-position voltage type relay X in sequence3DC power supply negative electrode voltage U of protection deviced-；
And the positive voltage U of the DC power supply of the protection deviced+Respectively connected DC offset latching start relay Xq2DC offset latching return relay XfSaid DC offset latching start relay Xq2Latching return relay X with DC offsetfParallel connection and two-position voltage type relay X connected with the other end in sequence2DC power supply negative electrode voltage U of protection deviced-；
The protection device is used for protecting the positive voltage U of the direct-current power supplyd+And the protection action relay TJ in the protection outlet loop is also connected.
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