CN103346535A - Doubling differential protection method for converter transformer - Google Patents

Abstract

The invention relates to a doubling differential protection method for a converter transformer. Current values obtained through measurement of a grid-side current transformer of the converter transformer are adopted in a first layer of protection, current values obtained through calculation of the other grid-side current transformer and in-line currents of the converter transformer are adopted in the other layer of protection, and real doubling protection is achieved under the condition that existing configuration is not changed.

Description

A kind of change of current becomes dualization differential protecting method

Technical field

The present invention relates to the converter transformer of extra-high voltage DC transmission system, particularly its dualization differential protecting method.

Background technology

The current conversion station of extra-high voltage direct-current system, each utmost point of standing claims 30 ° six pulse conversion device unit to form by two phase places mutually, two respectively corresponding converter transformers of inverter unit, one is the star change, another is that the star angle becomes.

In order to make protection system more safe and reliable, the change of current becomes protection usually needs to adopt multipleization scheme, as dualization protection (first heavy and second weight).Theoretically, two cover protections should be separate, namely determines to carry out to move from data acquisition, calculating and all should adopt independently element, thereby play the purpose of dualization protection.Be the complete situation of instrument transformer configuration as Fig. 1, suppose to have two cover protection A, B, become for each change of current so, all need 4 instrument transformers (becoming T2 with star is example, and Fig. 2, Fig. 3, Fig. 4 all are that example is introduced with T2, and it is corresponding with T2 that the star angle becomes the T1 situation).Each sends into same protection system to the equal signal of instrument transformer (net side and valve side are a pair of).For first heavy or second weight, star transformer differential protection implementation is:

$I_{\mathrm{op}}=|{\stackrel{\·}{I}}_{1y}+{\stackrel{\·}{I}}_{2y}|$ $I_{\mathrm{res}}=|{\stackrel{\·}{I}}_{1y}+{\stackrel{\·}{I}}_{2y}|/2$

Wherein, I _OpBe differential current, I _ResBe stalling current,

For star becomes current on line side,

For star becomes current on valve side.

For first heavy or second weight, star angle transformer differential protection implementation is:

$I_{\mathrm{op}}=|{\stackrel{\·}{I}}_{1\mathrm{\Δ}}+{\stackrel{\·}{I}}_{2\mathrm{\Δ}}|$ $I_{\mathrm{res}}=|{\stackrel{\·}{I}}_{1\mathrm{\Δ}}+{\stackrel{\·}{I}}_{2\mathrm{\Δ}}|/2$

Wherein, I _OpBe differential current, I _ResBe stalling current,

For the star angle becomes current on line side,

For the star angle becomes current on valve side.

But, disposes more instrument transformer and also mean more purchase cost and maintenance cost, and instrument transformer itself being the fault element that dispose more manyly, the fault point is more many, line node is more many, and system complexity and stability problem also can be very outstanding; So in the real system, configuration is situation as shown in Figure 1.

Existing configuration mode as shown in Figure 2, each change of current becomes current transformer of net side configuration, the valve side all disposes two current transformers.Because acquisition elements is identical, existing dualization scheme only actually is to have adopted different criterion computing elements, if acquisition elements goes wrong, just can not play a protective role.So in fact existing dualization scheme only is a kind of redundancy scheme, it is not real dualization protection.

Summary of the invention

The purpose of this invention is to provide a kind of change of current and become dualization differential protecting method, in order to solve the problem that prior art can not realize real dualization protection.

For achieving the above object, the solution of the present invention is: a kind of change of current becomes dualization differential protecting method, becomes for change of current, and the current value that itself current on line side instrument transformer measurements obtained is used for one and heavily protects as the heavy current on line side signal of protection; The value that the current value that the current on line side instrument transformer measurement that another change of current is become obtains and inlet wire current value calculate through vector addition as the current on line side signal of another heavy protection, is used for another heavy protection.

When alternating-current field adopted 3/2 mode of connection, the killer switch electric current by the inlet wire both sides calculated described inlet wire current.

The solution of the present invention; the one heavy protection current value that adopted the current on line side instrument transformer measurement of change of current change itself to obtain; and another heavy current value that has adopted the current on line side instrument transformer that become by another change of current and inlet wire current to calculate; dispose under the constant situation existing; the input variable that the duplicate protection system adopts has realized real dualization protection from different acquisition elements.

Further, when alternating-current field adopted 3/2 wiring, the present invention had adopted 3/2 pull-switch electric current to reflect inlet wire current, does not increase configuration, so do not need to increase any cost, only relied on existence conditions just to realize dualization protection

Description of drawings

Fig. 1 is the theoretical complete configuration of multipleization protection;

Fig. 2 is existing multipleization scheme;

Fig. 3 is one embodiment of the present invention;

Fig. 4 is the execution mode of alternating-current field when adopting 3/2 wiring;

Fig. 5 is that star becomes the protection flow process.

Embodiment

The present invention will be further described in detail below in conjunction with accompanying drawing.

Be illustrated in figure 3 as a kind of execution mode of dualization differential protection scheme of the present invention, become T2 for the change of current, the current value that the current on line side instrument transformer measurement of itself obtains is as the first current on line side signal of heavily protecting A, do difference with the current value that current on valve side instrument transformer TA7.1 itself measures, be used for first and heavily protect A; The change of current is become the value that current value that the current on line side instrument transformer TA3.1 of T1 measures and inlet wire current value I calculate through vector addition; as the second current on line side signal of heavily protecting B; do difference with the current value that current on valve side instrument transformer TA7.2 itself measures, be used for second and heavily protect B.

For T1, also has double protection.The current value that the current on line side instrument transformer TA3.1 of itself measures is done difference as the first heavy current on line side signal of protection with the current value that current on valve side instrument transformer measurements itself obtains, and is used for first and heavily protects; The change of current is become the value that current value that the current on line side instrument transformer measurement of T2 obtains and inlet wire current value I calculate through vector addition; as the second current on line side signal of heavily protecting; do difference with the current value that current on valve side instrument transformer measurements itself obtains, be used for second and heavily protect.

Inlet wire current I can obtain by metering system; also can obtain by calculating; when adopting 3/2 wiring at alternating-current field; (still be that example describes with T2 as shown in Figure 4; the guard method of T1, flow process are corresponding with T2); the change of current becomes second of T2 heavily to be protected among the B, and the calculating of its current on line side signal has been used the net side of alternating-current field 3/2 pull-switch electric current and T1 and measured electric current.

$I_{\mathrm{op}}=|{\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2-{\stackrel{\·}{I}}_{1\mathrm{\Δ}}+{\stackrel{\·}{I}}_{2y}|$ $I_{\mathrm{res}}=|{\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2-{\stackrel{\·}{I}}_{1\mathrm{\Δ}}-{\stackrel{\·}{I}}_{2y}|/2$

Wherein, I _OpBe differential current, I _ResBe stalling current,

Be respectively alternating-current field 3/2 pull-switch electric current,

For the star angle becomes current on line side,

For star becomes current on valve side.Flow process comprises as shown in Figure 5: step 1. measuring switch electric current 1, switching current 2, star angle become current on line side and star becomes current on valve side; Step 2. is calculated differential current; Step 3. judges that whether differential current is greater than definite value; Step 4. does not satisfy, and returns step 2; Satisfy, enter step 5; Step 5. protection tripping operation.

Claims (2)

1. a change of current becomes dualization differential protecting method, it is characterized in that, becomes for change of current, and the current value that itself current on line side instrument transformer measurements obtained is used for one and heavily protects as the heavy current on line side signal of protection; The value that the current value that the current on line side instrument transformer measurement that another change of current is become obtains and inlet wire current value calculate through vector addition as the current on line side signal of another heavy protection, is used for another heavy protection.

2. a kind of change of current according to claim 1 becomes dualization differential protecting method, it is characterized in that, when alternating-current field adopted 3/2 mode of connection, the killer switch electric current by the inlet wire both sides calculated described inlet wire current.

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