JPS62196018A - Differential relay for transformer protection - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential relay device for protecting a transformer.

[Conventional technology]

Fig. 3 is a block diagram showing a conventional differential relay device for protecting transformers.
R is the protected transformer, TC is the on-load tap changer, RIO
,...R2, R1, C, LL, L2. ..., Ll
o is the tap position, for example the maximum tap RIO is +15%
, the minimum tap LIO is 115 steps, and 1 tap is 1.5 steps.

CTH is the high voltage side current transformer, CTL is the low voltage side current transformer, NH is the CTHOCT ratio, NL is the CT ratio of CTL, 10 is the ratio differential relay (hereinafter simply referred to as differential relay), RCH is the high voltage side suppression coil, RCL is the low voltage side suppression coil, OC is the operating coil, 1 is the ratio differential element, vH is the high voltage side voltage, v
L is the low voltage side voltage, IIH is the high voltage side primary current, IIL is the low voltage side primary current, I2H is the high voltage side secondary current, IRH is the high voltage side relay input current, IRL is the low voltage side relay input current, A
CT is a compensating current transformer with the number of turns on the primary side n1 and the number of turns on the secondary side n2, so that when the on-load tap changer TC is at the center position C, the high voltage side relay input current IRH and the low voltage side relay input current IRL are equal. The purpose is to convert the high voltage side secondary current I2H into a high voltage side primary current IRH of an appropriate value. FO is an external failure point, and FI is an internal failure point.

Next, the operation will be explained. Note that FIG. 4 is a diagram showing an example of ratio differential characteristics of a conventional differential relay.

(b) When the on-load current tap changer (hereinafter simply tap changer) TC is at the center position C when it is in good condition or when there is an external failure FO, the high voltage side relay input current IRH and the low voltage side relay input current I
Compensated current transformation is carried out so that RL is equal, and the operating coil O
The differential current ID of C is zero, for example, for both the load current (low voltage side relay input current IRL) of 100% and the external fault current (low voltage side relay input current IRL of 1000%).

(b) When the tap changer TC is at the maximum tap R10+15 in normal condition or external failure FO, the high voltage side relay input current IRH is the low voltage side relay input current 1
1 (15% smaller than L, 15% smaller than operating coil OC)
% differential current ID is flowing. As shown in Figure 4, the ratio characteristic of the ratio differential element 1 is 15% due to the fluctuation of the tap changer TC, plus an additional 5% margin (considering the error of the current transformer and the error of the differential relay). It is designed to operate at 20%. That is, the load current (low voltage side relay input current IR
L) 20% differential current ID for 100%,
Also, external fault current (low voltage side relay input current IRL) 1
000%, the ratio differential element 1 does not output because it has a characteristic of operating when a 200% differential current ID flows.

(c) When the tap changer TC is at the minimum tap LIO-15 in normal condition or external failure FO, the high voltage side relay input current IRH is the low voltage side relay input current I
It is 15 inches larger than RL, and the operating coil OC is 15 inches larger.
% differential current is flowing, but since the ratio characteristic of the ratio differential element 1 is 20chi, the ratio differential element 1 does not output as in (b) above.

) Tap changer TC is at center position C when internal failure occurs.
When the differential current ID associated with the tap changer 10 position is zero, the internal fault current IF flowing from the power supply PS to the fault point FI is 20% or more compared to 100% of the load current 1 outputs.

(e) Internal failure When the tap changer TC is at the maximum tap R10 + 15% position at FI, a differential current ID -15% due to the tap changer 10 position is generated at a load current of 100, so the load current and internal failure When the power factor angles of the currents IP are equal, the ratio differential element 1 outputs when the internal fault current IF from the power supply PS is 20%+15%=35% or more.

(F) When the internal failure FI occurs and the tap changer TC is at the minimum tap LIO-15 position, the load current is 100% and the differential current ID +15% due to the tap changer position 10 is generated, so the load current and internal When the power factor angles of the fault currents IP are equal, the ratio differential element 1 outputs when the internal fault current IF from the power supply PS is 20%-15%=5% or more.

[Problems to be Solved by the Invention] Since the conventional differential relay device for protecting a transformer is configured as described above, if the fluctuation of the tap changer TC is ±15 inches, the ratio differential element 20 by adding margin to the ratio characteristic of 1.
Therefore, the sensitivity to internal failures varies depending on the position of the tap changer TC, such as 5chi, 20%, and 35chi as shown in (e) and (f) above, and the sensitivity is low. However, there was a problem in that the detection of symptomatic failures was not sufficient.

This invention was made in order to solve the above-mentioned problems, and its purpose is to obtain a differential relay device for protecting a transformer that has constant sensitivity regardless of the position of the tap changer TO and has high sensitivity. shall be.

[Means for solving problems]

The differential relay device for protecting a transformer according to the present invention is provided when the ratio of the magnitude of the high voltage side relay input current 11 (H) to the magnitude of the low voltage side relay input current IRL is below a predetermined value. A first comparison circuit that detects that the ratio is equal to or higher than a predetermined value is provided, and a second comparison circuit that detects that the ratio is equal to or higher than a predetermined value is provided. Equipped with a current conversion circuit that automatically adjusts the relay input current to reduce the high-voltage side relay input current when the value exceeds the value, and cancel the differential current ID caused by the position fluctuation of the tap changer TC. It is.

[For production]

The differential relay in this invention is, for example, a tap changer TC.
Suppose that moves by one tap from the center position C, and the high voltage side relay input current IRH increases correspondingly to this one tap, the second comparison circuit that detects the predetermined value or more outputs to the current conversion circuit, The current conversion circuit converts the high voltage side relay input current I
Decrease RH.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

However, the same reference numerals are given to the same constituent members as in FIG. 3, and the explanation thereof will be omitted as appropriate.

In Figure 1, one tap on the tap changer TC is 1.5
It changes from time to time. R is a condition where the ratio of the magnitude of the high voltage side relay input current IRH to the magnitude of the low voltage side relay input current IRL is less than a predetermined value, that is, (100% - 1.5/2%
) = 99.25% or less, and L is a first comparison circuit that detects that the ratio of the magnitude of the high voltage side relay input current IRH to the magnitude of the low voltage side relay input current IRL is greater than or equal to a predetermined value, that is, ( 100%+1.5/2'%'')=1
This is a second comparison circuit that detects that it is 00.75% or more. Here, for tap changer T C1.5%, 1
．． 5/2 < The reason for closing is to ensure that movement of one tap is detected.

2 is a current conversion circuit, and once it receives an output from the first comparator circuit R, it goes from tap SC to tap SR1, and when it receives an output again, it goes from tap SRI to tap SR2, and so on.
The output current of the compensation current transformer ACT is changed to 1 of the tap changer TC.
Increase brightness in steps equal to 1.5% tap. Similarly, upon receiving the output from the second comparison circuit, the tap SC
From tap SL1, then from tap SLI to tap SL
2, and so on, the output current of the compensation current transformer ACT is changed to 1.
The flow is reduced every 5% and supplied to the ratio operating element 1.

Next, the operation of the actuation relay having the above configuration will be explained.

FIG. 2 shows an example of the ratio differential characteristics of the differential relay 10. The ratio characteristics of the ratio differential element 1 are 1 tap of the tap changer TC
．． 5% plus a margin of 5% (accounting for current transformer errors and differential relay errors), i.e. 6.5% for load current (low voltage side current IRL) 100%, Also,
It has a characteristic that it operates when a differential current ID of 65% flows with respect to an external fault current (low voltage side current IRL) of 1000%.

(a) When the tap changer TC is at the center position C when the tap changer is in normal condition or when an external failure occurs at 20, the high voltage side relay input current IRH and the low voltage side relay input current I
Since RL are equal, the ratio of the magnitude of the high voltage side relay input current IRH to the magnitude of the low voltage side relay input current IRL is 100%, and the output from both the first and second comparators R and L is Therefore, the tap of the current converter 2 remains at the SC position, and the differential current ID is zero for both a load current of 100% and an external fault current of 1000%.

(b) Tap changer TC when in good condition or when an external failure occurs.
When is R1+1.5, the high voltage side relay input current IRH is the low voltage side relay input current I
It is 1.5 inches smaller than RL, and once the differential current ID is 1.5 inches.
5chi is generated, but the ratio characteristic of the ratio differential element 1 is 6.5chi as shown in FIG. 2, and the ratio differential element 1 does not output.

However, the ratio of the magnitude of the high voltage side relay manual current IRH to the magnitude of the low voltage side relay input current ■Rr is 98.
At 5%, the setting value of the first comparator R is less than 9925, so the first comparator R outputs, and the tap of the current conversion circuit 2 changes from the tap SC to the tap SRI. Then, the high voltage side input current IRH is increased by 1.5 inches, the high voltage side relay input current IRH and the low voltage side relay input current IRL are kept equal, and the differential current ID is returned to zero.

(/When the tag switch TC is currently healthy or when an external failure FO
is R2+3.0%, when the tap changer TC moves from position R1 to R2, the high voltage side relay input current IRH becomes 1.5% smaller than the low voltage side relay input current IRL, and once the differential current I
D is generated by 1.5 inches, but since the ratio characteristic of the ratio differential element 1 is 6.5%, the ratio differential element 1 does not output as in (b) above. However, the ratio of the magnitude of the high voltage side relay input current IRH to the magnitude of the low voltage side relay input current IRL is again 98.5%, and the setting value of the first comparator R is 99.2.
Since it is less than 5%, the first comparator R outputs the above (
b) Similarly, the tap of current conversion circuit 2 is changed from tap SRI to tag SR2, and again the high voltage side relay input current IR.
H is increased by 1.5 inches and the differential current ID is returned to zero.

b) When the tap changer TC is Ll-1.5% and L2-3% when the tap changer is in good condition or when there is an external failure FO However, since the second comparator detects it and the current conversion circuit 2 follows from tap SC to tap SLI and from tap SLI to tap SL2, the differential current ID is returned to zero.

(e) When an internal fault FI occurs and the tap changer TC is at the center position C, the differential current ID associated with the tap changer TC position is zero, and the internal fault current IP flowing from the power supply PS to the fault point FI is When the load is 6.5% or more compared to 1100chi, ratio differential element 1 outputs 0. ), 2), the differential current ID is generated by a maximum of ±1.5 only during the period until the tap follow-up operation of the current conversion circuit 2 is completed after the tap changer TC is moved. Therefore, if the power factor angle of the load current and the internal fault current IP are equal, the internal fault current IP from the power supply PS is 6.
5±1.5=Ratio differential element 1 outputs at 5 to 8 or more.

As explained above, in conventional differential relays, if the fluctuation range of the tap changer TC is ±15%, the detection sensitivity of internal failure IP is 5% to 35%. As is clear from the explanations in ) and (f), according to the present invention, a differential relay with high sensitivity of 5 to 8% and uniform sensitivity can be obtained, making it possible to detect slight faults in a transformer.

In the above explanation, the tap interval of the current conversion circuit 2 is set to 1.5 inches, which is equal to the tap interval of the tap changer TC, but the present invention is not limited to this, and any configuration may be made. be able to.

For example, the tap interval of the current conversion circuit 2 can be changed by the tap changer T.
In the case of configuring three channels with twice the tap interval of C, the detection sensitivities of the first and second comparison circuits R and L are set to (, 100-
3×g )=98% and (100+3X=)=102%
, and when the tag position of the tap changer TC moves by two taps, the current conversion circuit 2 follows by one tap. Accordingly, the ratio characteristic of ratio differential element 1 is 3% + 5
% (margin) = 8chi.

Further, in the above description, the current converter 2 is provided on the high voltage side relay input current (compensation current transformer output current) side, but it is also possible to provide it on the low voltage side relay input current side.

〔Effect of the invention〕

As described above, according to the present invention, the ratio between the high voltage side relay input current and the low voltage side relay input current is detected, and based on this result, either the high voltage side relay input current or the low voltage side relay input current is selected. The structure is configured to increase or decrease the differential current caused by the positional fluctuation of the tap changer, so the sensitivity is not affected by the positional fluctuation of the tap changer and is highly sensitive, making it possible to detect slight faults in the transformer. There are effects that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a differential relay device for protecting a transformer according to an embodiment of the present invention, FIG. 2 is a graph showing an example of ratio differential characteristics of the device shown in FIG. 1, and FIG. A block diagram showing a conventional differential relay device for protecting transformers.
FIG. 2 is a graph diagram showing an example of ratio differential characteristics of the one shown in the figure. 1 is a ratio actuation element, 2 is a current variable circuit, lO is a ratio actuation relay (actuation relay), R is a first comparator circuit, L is a second
, MTR is the protected transformer, TC is the current tap changer, CTH is the high voltage side current transformer, CTL is the low voltage side current transformer, ACT is the compensation current transformer, IRH is the high voltage side relay input current, IRL is the low voltage side relay input current. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A high voltage side current transformer and a low voltage side current transformer respectively provided on the high voltage side and low voltage side of the protected transformer having a current tap changer, and a compensation transformer connected to either one of the above two current transformers. A current transformer is provided between the compensation current transformer and the other one of the two current transformers, and the high voltage side relay input current and the low voltage side relay input current are supplied through the compensation current transformer. In a transformer protection differential relay device equipped with a ratio differential relay that adjusts the current of one of the relays, the current ratio of the high-voltage side relay input current and the low-voltage side relay input current is detected, and the current ratio is first and second comparison circuits that respectively detect whether it is below a predetermined value or above a predetermined value;
and a current conversion circuit that increases or decreases the output current of the compensation rectifier by steps corresponding to the switching steps of the current tap changer based on the detection results of the first and second comparison circuits. A differential relay device for protecting a transformer, characterized in that it is installed inside the transformer.