CN201886084U - Direct current insulation monitoring system capable of overcoming relaying protection misoperation - Google Patents

Abstract

The utility model relates to a direct current insulation monitoring system capable of overcoming relaying protection misoperation, comprising a balance bridge circuit and an unbalance bridge circuit. The balance bridge circuit consists of an anode balance-to-ground resistor and a cathode balance-to-ground resistor. The unbalance bridge circuit only consists of a cathode unbalance-to-ground resistor and a cathode unbalance-to-ground resistor selector switch. When insulation monitoring is carried out, through switching the unbalance bridge circuit, the voltage to ground of a positive bus and a negative bus is measured, and the insulation resistance of the positive bus and the negative bus is calculated. When the anode of a relaying production system is grounded, insulation monitoring is performed at this moment, and switching the unbalance bridge circuit can not cause the relaying protection misoperation since the unbalance bridge circuit only consists of the cathode unbalance-to-ground resistor and the cathode unbalance-to-ground resistor selector switch.

Description

Can overcome the D.C. isolation monitoring system of protective relaying maloperation

Technical field

The utility model relates to the D.C. isolation monitoring system that can overcome protective relaying maloperation, belongs to direct current IT system insulating monitoring field.

Background technology

The straight-flow system of generating plant and transformer station provides power supply for control, protection, signal and aut.eq., and for the continuity and the reliability that guarantee to power, straight-flow system generally is designed to isolated neutral system, i.e. IT system.According to the designing requirement of power engineering straight-flow system, need carry out insulating monitoring to the direct current IT system.

Present most of insulation monitoring and warning device is to carry out insulating monitoring by the method that balance bridge combines with uneven bridge.By switching unbalanced bridge, measure both positive and negative polarity magnitude of voltage over the ground when uneven bridge is in different conditions, utilize the both positive and negative polarity voltage-to-ground value of measuring to calculate positive and negative busbar insulating resistance.

When straight-flow system generation one point earth, generally can not influence the normal operation of straight-flow system, but know that from the accident information of generating plant and transformer station feedback in recent years straight-flow system generation one point earth also protective relaying maloperation can take place.According to theoretical analysis and simulation test, during the straight-flow system one point earth, protective relaying maloperation is caused by insulation monitoring and warning device sometimes.

Below the protective relaying maloperation that causes owing to insulation monitoring and warning device is carried out brief analysis.

As Fig. 2, insulating monitoring electric bridge 1 is made of balance bridge circuit 11 and uneven bridge circuit 12, establishes R ₁=R ₂=R ₀, R ₃=R ₄=R _CSupposing the system exists insulation to descend 2, and anodal insulation against ground resistance is R ₊, negative pole insulation against ground resistance is R _-The course of work of insulating monitoring electric bridge 1 is: K switch ₂Closure, K switch ₁Disconnect, measure anodal voltage-to-ground U ₁₊With negative pole voltage-to-ground U _1-K switch ₁Closure, K switch ₂Disconnect, measure anodal voltage-to-ground U ₂₊With negative pole voltage-to-ground U _2-, then can solve anodal insulation against ground resistance R ₊With negative pole insulation against ground resistance R _-:

$R_{+}=\frac{R_0{R}_C(U_{1-}-U_{2-})}{R_0{U}_{2-}-R_C(U_{1-}-U_{2-})};$ $R_{-}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+})}{R_0{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}-R_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+})}$

The relay protection system 3 that is connected to direct supply is by relay protection contact K ₀With execution coil R _JConstitute, according to the actual conditions of transformer station, protection contact K ₀Generally be in indoorly, carry out coil R _JGenerally be in the open air, connecting terminal K ₀With execution coil R _JCircuit, it is longer promptly to put 31 and 32 distances, adds that outdoor environment is abominable relatively, the probability that ground connection is taken place at this section is higher.When this section circuit generation earth fault, as Fig. 3.Carry out coil R this moment _JOn voltage U _RJ1For:

$U_{\mathrm{RJ}1}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}}U$

Carry out coil R _JSpecified operation voltage be U _e, establish U this moment _RJ1＜U _e, protective relaying maloperation can not take place then.

In order to measure the positive and negative busbar insulating resistance value, need to switch electric bridge, work as K switch ₂Closure, K switch ₁During disconnection, carry out coil R _JOn voltage U _RJ2For:

$U_{\mathrm{RJ}2}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}+\frac{1}{R_c}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}+\frac{1}{R_c}}U$

U _RJ2＞U _RJ1, work as U _RJ2〉=U _eThe time, then protective relaying maloperation can take place.

If busbar voltage U=220V, the specified operation voltage of carrying out coil is 50% of busbar voltage, i.e. U _e=110V, R _J=20k Ω; R ₁=R ₂=R ₃=R ₀=R _c=30k Ω; The bus insulation resistance R ₊=30k Ω, R _-=∞, then:

$U_{\mathrm{RJ}1}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}}U=\frac{\frac{1}{30000}+\frac{1}{30000}}{\frac{1}{30000}+\frac{2}{30000}+\frac{1}{20000}}\&times;220\&ap;97.8V$

U _RJ1＜U _e

$U_{\mathrm{RJ}2}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}+\frac{1}{R_c}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}+\frac{1}{R_c}}U=\frac{\frac{1}{30000}+\frac{1}{30000}+\frac{1}{30000}}{\frac{1}{30000}+\frac{2}{30000}+\frac{1}{20000}+\frac{1}{30000}}\&times;220=120V$

U _RJ2＞U _e

Protective relaying maloperation just can take place in this moment.

The utility model content

The purpose of this utility model provides a kind of D.C. isolation monitoring system that overcomes protective relaying maloperation, when carrying out insulating monitoring, can overcome protective relaying maloperation.

Technical solution of the present utility model is:

A kind of D.C. isolation monitoring system that overcomes protective relaying maloperation; comprise balance bridge circuit and uneven bridge circuit two parts; the balance bridge circuit is made up of the balance resistance that is connected on the balance resistance between straight-flow system positive pole and the ground and be connected between straight-flow system negative pole and the ground, it is characterized in that:

Described uneven bridge circuit only is made of negative pole unbalanced to ground resistance, negative pole unbalanced to ground resistance change-over switch, and negative pole unbalanced to ground resistance is connected in series with negative pole unbalanced to ground resistance change-over switch, and is connected between straight-flow system negative pole and the ground.

Further:

Described negative pole unbalanced to ground resistance is single resistance.

Described negative pole unbalanced to ground resistance is made up of through series connection or through parallel connection or through series-parallel form several resistance.

Described negative pole unbalanced to ground resistance change-over switch is mechanical switch or electronic switch.

The utility model adopts above-mentioned bridge diagram technology to carry out the D.C. isolation monitoring, can finish the calculating of both positive and negative polarity insulation against ground resistance, overcomes protective relaying maloperation simultaneously.

Description of drawings

Fig. 1 is the theory diagram of the utility model insulating monitoring system, and uneven bridge circuit shown in the figure has only negative pole unbalanced to ground resistance, and relay protection system is unearthed.

Fig. 2 is the theory diagram of existing insulating monitoring bridge diagram, and the existing negative pole unbalanced to ground of uneven bridge circuit shown in figure resistance has anodal unbalanced to ground resistance again, and relay protection system is unearthed.

Fig. 3 is the theory diagram of existing insulating monitoring bridge diagram, and the existing negative pole unbalanced to ground of uneven bridge circuit shown in figure resistance has anodal unbalanced to ground resistance again, relay protection system ground connection.

Fig. 4 is the theory diagram of the utility model insulating monitoring bridge diagram, and uneven bridge circuit shown in the figure has only negative pole unbalanced to ground resistance, relay protection system ground connection.

Embodiment

The utility model relates to the D.C. isolation monitoring system that can overcome protective relaying maloperation.

The theory diagram of embodiment such as Fig. 1, insulating monitoring bridge diagram 1 is made of balance bridge circuit 11 and uneven bridge circuit 12 two parts.Balance bridge circuit 11 is made of anodal balanced to ground resistance R 1 and negative pole balanced to ground resistance R 2, anodal balanced to ground resistance R 1 connection bus anodal and ground, negative pole balanced to ground resistance R 2 connection bus negative poles and ground.R ₁＝R ₂＝R ₀＝30kΩ。Anodal balanced to ground resistance R 1 can be single resistance, also can be series, parallel or series-parallel mixed form of several resistance; Negative pole balanced to ground resistance R 2 can be single resistance, also can be series, parallel or series-parallel mixed form of several resistance.

Uneven bridge circuit 12 only is made of negative pole unbalanced to ground resistance R 3, negative pole unbalanced to ground resistance change-over switch K1.Negative pole unbalanced to ground resistance R 3 is connected in series with negative pole unbalanced to ground resistance change-over switch K1, and is connected between bus negative pole and the ground.R ₃＝R _C＝30kΩ。Negative pole unbalanced to ground resistance R 3 can be single resistance, also can be series, parallel or series-parallel mixed form of several resistance; Negative pole unbalanced to ground resistance change-over switch K1 can be a mechanical switch, also can be electronic switch.

The course of work of this circuit is: when negative pole unbalanced to ground resistance change-over switch K1 disconnects, measure the anodal voltage-to-ground U of bus ₁₊With bus negative pole voltage-to-ground U _1-When negative pole unbalanced to ground resistance change-over switch K1 is closed, measure the anodal voltage-to-ground U of bus ₂₊With bus negative pole voltage-to-ground U _2-Then can solve anodal insulation against ground resistance R ₊With negative pole insulation against ground resistance R _-:

$R_{+}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})}{R_0{U}_{1-}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})};$ $R_{-}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}{R_0{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379770100011.png,HSA00000379770100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379770100022.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}$

If busbar voltage is 220V, carry out coil R _JSpecified operation voltage be 50% of busbar voltage, i.e. U _e=110V, R _J=20k Ω; The bus insulation resistance R ₊=30k Ω, R _-=∞; Fig. 4 is seen in certain anodal single-point grounding of protective relay constantly, carries out coil R this moment _JOn voltage U _RJ1For:

$U_{\mathrm{RJ}1}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}}U=\frac{\frac{1}{30000}+\frac{1}{30000}}{\frac{1}{30000}+\frac{2}{30000}+\frac{1}{20000}}\&times;220\&ap;97.8V$

U _RJ1＜U _e

Closed negative pole unbalanced to ground resistance change-over switch K1 carries out coil R _JOn voltage U _RJ2For:

$U_{\mathrm{RJ}2}=\frac{\frac{1}{R_{+}}+\frac{1}{R_0}}{\frac{1}{R_{+}}+\frac{1}{R_{-}}+\frac{2}{R_0}+\frac{1}{R_J}+\frac{1}{R_c}}U=\frac{\frac{1}{30000}+\frac{1}{30000}}{\frac{1}{30000}+\frac{2}{30000}+\frac{1}{20000}+\frac{1}{30000}}\&times;220=80V$

Because U _RJ2＜U _RJ1＜U _eSo relay protection system 3 can not cause protective relaying maloperation because of the switching of uneven bridge circuit 12 in the insulating monitoring electric bridge 1.

Claims (4)

1. D.C. isolation monitoring system that can overcome protective relaying maloperation; comprise balance bridge circuit and uneven bridge circuit two parts; the balance bridge circuit is made up of the balance resistance that is connected on the balance resistance between bus positive pole and the ground and be connected between bus negative pole and the ground, it is characterized in that:

Described uneven bridge circuit only is made of negative pole unbalanced to ground resistance, negative pole unbalanced to ground resistance change-over switch, and negative pole unbalanced to ground resistance is connected in series with negative pole unbalanced to ground resistance change-over switch, and is connected between bus negative pole and the ground.

2. the D.C. isolation monitoring system that overcomes protective relaying maloperation as claimed in claim 1 is characterized in that:

Described negative pole unbalanced to ground resistance is single resistance.

3. the D.C. isolation monitoring system that overcomes protective relaying maloperation as claimed in claim 1 is characterized in that:

Described negative pole unbalanced to ground resistance is made up of through series connection or through parallel connection or through series-parallel form several resistance.

4. the D.C. isolation monitoring system that overcomes protective relaying maloperation as claimed in claim 1 is characterized in that:

Described negative pole unbalanced to ground resistance change-over switch is mechanical switch or electronic switch.

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