CN102486496A - Direct current insulation monitoring system and method capable of overcoming relay protection maloperation - Google Patents

Abstract

The invention relates to a direct current insulation monitoring system and method capable of overcoming relay protection maloperation. The system comprises a balanced bridge circuit and an unbalanced bridge circuit, wherein the balanced bridge circuit comprises a positive balancing resistor to ground and a negative balancing resistor to ground; and the unbalanced bridge circuit only comprises a negative unbalancing resistor to ground and a change-over switch of the negative unbalancing resistor to ground. When insulation monitoring is carried out, the insulation resistance of the positive and negative busbars is computed by changing over the unbalanced bridge circuit and measuring the voltages to ground of the positive and negative busbars; and when a relay protection system is subjected to positive grounding, insulation monitoring is carried out at the moment, and relay protection maloperation can not be caused by changing over the unbalanced bridge circuit as the unbalanced bridge circuit only comprises the negative unbalancing resistor to ground and the change-over switch of the negative unbalancing resistor to ground.

Description

Can overcome the D.C. isolation monitoring system and the method for protective relaying maloperation

Technical field

The present invention relates to overcome the D.C. isolation monitoring system and the method for protective relaying maloperation, belong to direct current IT system insulating monitoring field.

Background technology

The straight-flow system of generating plant and transformer station is that control, protection, signal and aut.eq. provide power supply, and for the continuity and the reliability that guarantee to supply 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 through the method that balance bridge combines with uneven bridge.Through 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 that generating plant and transformer station in recent years feed back 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.

Carry out brief analysis in the face of the protective relaying maloperation that causes owing to insulation monitoring and warning device down.

Like Fig. 2, insulating monitoring electric bridge 1 is made up 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 ₁Break off, measure anodal voltage-to-ground U ₁₊With negative pole voltage-to-ground U _1-K switch ₁Closure, K switch ₂Break off, 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 _-:

$R_{+}=\frac{R_0{R}_C(U_{1-}-U_{2-})}{R_0{U}_{2-}-R_C(U_{1-}-U_{2-})};$ $R_{-}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+})}{R_0{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}-R_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+})}$

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, like 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.

Summary of the invention

The purpose of this invention is to provide a kind of D.C. isolation monitoring system and method that overcomes protective relaying maloperation, when carrying out insulating monitoring, can overcome protective relaying maloperation.

Technical solution of the present invention 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:

Said uneven bridge circuit only is made up 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:

Said negative pole unbalanced to ground resistance is single resistance.

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

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

The course of work of this system is: when negative pole unbalanced to ground resistance change-over switch is broken off, 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 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 _-:

$R_{+}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})}{R_0{U}_{1-}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})};$ $R_{-}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}{R_0{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}$

In the formula: R ₀Be the resistance of balanced to ground resistance, R _CResistance for negative pole unbalanced to ground resistance.

If carry out coil R _JSpecified operation voltage be U _e, Fig. 4 is seen in certain anodal single-point grounding of protective relay constantly, carries out coil R this moment _JOn voltage U _RJ1For:

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

If U _RJ1＜U _e, malfunction can not take place in protective relay.Closed negative pole unbalanced to ground resistance change-over switch K1 carries out coil R _JOn voltage be:

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

Because U _RJ2＜U _RJ1So 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.

The present invention adopts above-mentioned bridge diagram technology to carry out the D.C. isolation monitoring, can accomplish 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 insulating monitoring of the present invention 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 insulating monitoring bridge diagram of the present invention, and uneven bridge circuit shown in the figure has only negative pole unbalanced to ground resistance, relay protection system ground connection.

Embodiment

The present invention relates to overcome the D.C. isolation monitoring system and the method for protective relaying maloperation.

The theory diagram of embodiment such as Fig. 1, insulating monitoring bridge diagram 1 is made up of balance bridge circuit 11 and uneven bridge circuit 12 two parts.Balance bridge circuit 11 is made up of with negative pole balanced to ground resistance R 2 anodal balanced to ground resistance R 1, 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 up 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 breaks off, 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 _-:

$R_{+}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})}{R_0{U}_{1-}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-})};$ $R_{-}=\frac{R_0{R}_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}{R_0{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-}-R_c({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2+}{U}_{1-}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000379779100011.png,HSA00000379779100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1+}{U}_{2-})}$

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 (5)

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 up 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:

Said 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:

Said 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:

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

5. D.C. isolation monitoring method that can overcome protective relaying maloperation is characterized in that may further comprise the steps:

(1) breaks off negative pole unbalanced to ground resistance change-over switch, measure the anodal voltage-to-ground U of bus ₁₊With bus negative pole voltage-to-ground U _1-

(2) closed negative pole unbalanced to ground resistance change-over switch is measured the anodal voltage-to-ground U of bus ₂₊With bus negative pole voltage-to-ground U _2-

(3) be calculated as follows the anodal insulation against ground resistance R of bus+with bus negative pole insulation against ground resistance R-:

$R_{+}=\frac{R_0{R}_c(U_{1+}{U}_{2-}-U_{2+}{U}_{1-})}{R_0{U}_{1-}{U}_{2-}-R_c(U_{1+}{U}_{2-}-U_{2+}{U}_{1-})}$

$R_{-}=\frac{R_0{R}_c(U_{2+}{U}_{1-}-U_{1+}{U}_{2-})}{R_0{U}_{1+}{U}_{2-}-R_c(U_{2+}{U}_{1-}-U_{1+}{U}_{2-})}$

In the formula: R ₀Be the resistance of balanced to ground resistance, R _CResistance for negative pole unbalanced to ground resistance.

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