JPS62196019A - 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, R10
,...R2, R1, C, Ll , R2,..., Ll
o is the tap position, for example the maximum tap RIO is +15%
, the minimum tap LIO is -15, and one tap is a 1.5% step.

CTH is the high voltage side current transformer, CTL is the low voltage side current transformer, NH is the CT ratio of CTH, NL is the CTLOCT ratio, 10 is the ratio differential relay (hereinafter simply referred to as differential relay), and 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, VL
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, AC
T is a compensation current transformer with the number of turns on the primary side n1 and the number of turns on the secondary side n2,
When the on-load tap changer TC is at the center position C, the high voltage side secondary current I2H is converted to the high voltage side primary current IRH of an appropriate value so that the high voltage side relay input current IRH and the low voltage side relay human power current IRL are equal. It is for the purpose of 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 load current tap changer (hereinafter simply tap changer) TC is at the center position C when it is in good condition or when an external failure occurs, 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 100% of the load current (low-voltage side relay input current IRL) and 1000% of the external fault current (low-voltage side relay input current IRL).

(b) Tap changer TC when in good condition or when an external failure occurs.
is the maximum tap R10+15, the high voltage side relay input current IRH is the low voltage side relay input current I
15L% smaller than RL, and 15L% 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 calculated by adding an additional 5% margin (taking into account current transformer error and differential relay error) to 15% due to fluctuation of the tap changer TC. In other words, the load current (low voltage side relay input current IR
L) For 100%, the differential current ID is 20, and the external fault current (low voltage side relay input current IRL) 1
For 000%, the ratio differential element 1 does not output because it has a characteristic of operating when 200% differential '1 flow ID flows.

rC Tap changer TC when in good condition or when an external failure occurs.
When the minimum tap is LIO-15, the high voltage side relay input current IRH is the low voltage side relay input current I
15% larger than RL, operating coil 0CK15
% 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.

) 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 the load current. The differential element 1 outputs a ratio that is 2096 or more compared to 100%.

(e) Internal failure When FI is on and the tap changer TC is at the maximum tap R10+15 position, the load current is 100% and the differential current ID - 15% due to the tap changer TC position is generated, 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 IP from the power supply PS is 20%+15chi=35% or more.

(F) Internal failure FI When the tap changer TC is at the minimum tap LIO - 15% position, the load current is 100% and a differential current ID + 15% due to the tap changer TC position is generated, 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 IP from the power supply PS is 20115%=5chi 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%, the ratio differential element 20 by adding margin to the ratio characteristic of 1.
Therefore, the sensitivity to internal failure is 5%, 20%, 35% as shown in (e) and (e) above.
The problem is that it fluctuates depending on the position of the tap changer TC and the sensitivity is low, making it difficult to detect faulty symptoms sufficiently.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a highly sensitive differential relay device for protecting a transformer, which has constant sensitivity regardless of the position of the tap changer TC. shall be.

[Means for solving problems]

The differential relay device for protecting a transformer according to the present invention detects that a differential current of a predetermined value or more is flowing in the high voltage side relay input current IRH in a predetermined current direction inside the differential relay, and When the directional element R outputs, it is provided with a directional element R that reduces the high voltage side relay input current IRH, and also detects that a differential current ID of a predetermined value or more is flowing in the opposite direction to the above, and The high voltage relay input current IRH is provided with a directional element that increases the high voltage relay input current IRH when the current is output. Then, the differential current ID due to the position fluctuation of the tap changer TC
A current converter circuit 2 is provided which automatically adjusts these relay input currents so as to cancel the current.

[For production]

In the differential relay according to the present invention, for example, if the tapper switch TC moves one tap away from the center position, the high voltage side relay input current IRH increases, and the differential current ID flows, the above-mentioned predetermined current direction, a predetermined value or more The directional element R or L that detects outputs it to the current conversion circuit 2, and the current conversion circuit 2 reduces the high voltage side relay input current IRH.

〔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, R is the current direction of the differential current - ΔID
In the direction of , if one tap of the tap changer TC is 1.5 taps, then ↓ x 1.5 taps = directional element that detects flow of 0.75% or more, and L is the difference. The current direction of dynamic current is +ΔID direction, and its magnitude is also 0.7
This is a direction element that detects when the flow is 54 or more.

Here, one tap of the tap changer TC is 1.5 taps, and the sensitivity of the directional element is set to 0.75% because
This is to reliably detect the movement of one tap. 02 is a current conversion circuit, and once it receives an output from the first direction element R, it goes from tap SC to tap SRI, and when it receives an output again, it goes from tap SRI to tap SR2. , the output current of the compensating current transformer ACT is increased in equal steps to 1.5% per tap of the tap changer TC. Similarly, upon receiving the output from the second directional element, the output current of the compensating current transformer ACT is decreased every 1.5 times from tap SC to tap SLI, and from tap SLI to tap SL2. It flows and supplies the ratio operating element 1.

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

Figure 2 shows an example of the ratio differential characteristic of the differential relay IO, and the ratio characteristic of the ratio differential element 1 is 1 of one tap of the tap changer TC.
．． The load current (low voltage side current I
It has a characteristic that it operates when a differential current ID of 6.5% flows for 100% (RL), and 65% for an external fault current (low voltage side current IRI) of 100%.

(b) When the tap changer TC is in good condition or when there is an external failure FO.
When is at center position C, high voltage side relay input current IRH and low voltage side relay input current I
Since RL are equal, the differential current ID is zero. Therefore, there is no output from either the first or second directional elements R, L, the tap of the current converter 2 remains at position C, and the ratio differential element 1 also does not output.

(b) When the tap changer T is in good condition or when there is an external failure FO.
When C 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 is generated by 1°5% in the direction from 1Δ in Fig. 1, the ratio differential element 1
Since the ratio characteristic of is 6.5% as shown in Figure 2,
Ratio differential element 1 does not output.

However, since the magnitude of the differential current -ΔID is 185 inches and the sensitivity of the directional element R is 0.75 inches or more, the directional element R
is output, the tap of the current conversion circuit 2 changes from tap SC to tap SRI, and the high voltage side relay input current IRH becomes 1.
The current is increased by 5, and the differential current -ΔID is returned to zero.

(c) Tap changer TC when in good condition or when external failure FO
When tap changer TC moves from position R1 to R2 when is R2 + 3%, the high voltage side relay input current IRH becomes 1.5% smaller than the low voltage side relay input current IRL again, and once the differential current becomes as shown in Fig. 1. 1.5% occurs in the direction of one ΔID, but since the ratio characteristic of the ratio differential element 1 is 6.5%, the ratio element 1 does not output as in (b) above.

However, since the magnitude of the differential current -ΔID is 1.5% and the sensitivity of the directional element is 0.751 or more, the first directional element R outputs, and the current conversion circuit as in (b) above 2
Tap SRI becomes tap SR2, and the high voltage side relay input current IRH is increased by 1.5% again, resulting in a differential current -Δ
The ID is returned to zero.

b) When the tap changer TC is Ll -1, 5 and R2 - 3 when the tap changer is in good condition or when an external failure R0 occurs, the differential current will once change to the value shown in Figure 1, similar to (b) and (c) above. However, since the second directional element detects it and the current conversion circuit 2 follows from tap SC to tap SLI and tap SL2, the differential current +ΔID is zero. has been returned to.

(e) When the internal failure FI occurs and the tap changer TC is at the center position C, the differential current associated with the tap changer TC position is zero, and the power supply P
When the internal fault current IP flowing from S to the fault point FI is 6.5% or more compared to 100% of the load current, the ratio differential element 1
outputs.

(v) When the tap changer TC is in a position other than the center position C due to an internal failure FI As stated in (b), (c), and (c) above, the tap follow-up operation of the current conversion circuit 2 after the tap changer TC is moved. The differential current (-ΔID) or (+ΔID
) occurs up to ±1.5 inches. 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 = 5% to 8 or more, and the ratio differential element 1 outputs do.

As explained above, in conventional differential relays, if the variation range of the tap changer TC is ±15 inches, the detection sensitivity for internal failure IP is 5 to 35%, but
According to the present invention, as is clear from the explanation of (to),
A differential relay with uniform sensitivity and high sensitivity of 5 to 8% can be obtained.
It becomes possible to detect minor faults in transformers.

In addition, in the above explanation, an example was explained in which the tap interval is 1.5%, which is equal to the tap interval of the tap changer TC of the current conversion circuit 2, but the configuration is not limited to this and may be configured as desired. can. For example, when the tap interval of the current conversion circuit 2 is configured to be 3%, which is twice the tap interval of the tap changer TC, the detection sensitivity of the first and second directional elements R and L is set to 3%.
%xg=zs, and when the tap position of the tap changer TC moves by 2 taps, the current conversion circuit 2 follows by 1 tap. Accordingly, the ratio characteristic of the ratio differential element 1 is set to 3,5% (margin) = 8%.

Further, in the above description, the current converter 2 is provided on the high voltage side relay input current (compensating current transformer output undercurrent) 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 differential current between the high voltage side relay input current and the low voltage side relay input current and the current direction are detected, and based on the results, the high voltage side relay input current and the low voltage side relay input current are detected. Increase one of the input currents,
Since the structure is configured to cancel the differential current caused by the positional fluctuation of the tap changer, the sensitivity is not affected by the positional fluctuation of the tap changer, and a highly sensitive device that can detect small faults in the transformer is obtained. It has the effect of

[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 a conventional ratio differential characteristic as shown in the figure. 1 is a ratio actuation element, 2 is a current conversion circuit, 10 is a ratio actuation relay, R is a first direction element, L is a second direction element, M
TR 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, and ΔID is the difference PJJ 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 differential relay device for protecting a transformer equipped with a ratio differential relay that adjusts the current of one of the relays, the differential current between the high-voltage side relay input current and the low-voltage side relay input current and the current direction are detected. A current 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 direction elements and the first and second direction elements. With the conversion circuit,
A differential relay device for protecting a transformer, characterized in that it is provided in the ratio differential relay.