JPS62207125A - Differential relay for protecting transformer - 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 transformer protection differential relay device that protects a transformer that can be tapped during load.

[Conventional technology]

Fig. 5 is a connection diagram showing a conventional transformer protection differential relay device. In Fig. 1, PS is the power supply of the power system, MTR is the protected transformer, TC is the on-load tap changer, and R1+R.
2*...R engineering. , C+ L 1r L 2 +...
Llo is the tap position.For example, maximum tap R.

is +15%, the minimum tap L1° is -15%, and the l tap is 1.5% step. CTH is the high voltage side current transformer of the transformer, CTL is the low voltage side current transformer, NH is the current transformation ratio of the high voltage side current transformer CTH, NL is the current transformation ratio of the low voltage side current transformer CTL, and 10 is the differential relay ( 12 below, simply called differential relay), RCH
is the high voltage side suppression circuit, RCL is the low voltage side suppression circuit, DF is the differential circuit, 1 is the ratio differential element, vH is the high voltage side voltage, vL is the low voltage side voltage, rlH is the high voltage side primary current, ILL is the low voltage side Primary current -12H is high voltage side secondary current - IRH is high voltage side relay input terminal, ■RL is low voltage side relay input terminal, I
DT is the tap varying differential current, IDF is the internal fault current, A
CTtli is a compensating current transformer with the number of turns on the primary side nl + the number of turns on the secondary side n2, and when the on-load tap changer TC is at the center position C, the high voltage side relay input terminal IRH and the low voltage side relay input terminal IRL
The high-voltage side secondary current I2H is converted to IRH so that they are equal.

FO is an external failure point and PI is an internal failure point. Further, FIG. 6 is a ratio differential characteristic diagram of the conventional differential relay device 10.

Next, the operation will be explained.

(a) On-load tap changer (hereinafter simply referred to as tap changer) T
C is the center position C, when the condition is healthy or when there is an external failure.

High voltage side relay input terminal IRH and low voltage side relay input terminal I
The differential current of the current transformer DF of the compensation current transformer ACT to make RL equal is % even if the load current (low voltage side relay input terminal fRL) is 100%, if the slight error of the current transformer is ignored. Further, even when the external fault current (low voltage side relay input terminal IRL) is 1000%, each is zero.

(b) The tap changer TC is at the maximum tap R10 position (+
15%, when healthy or external failure 20:00.

High voltage side relay input terminal IRH is low voltage side relay input terminal I
15% smaller than RL, and -15% tap fluctuation differential current I due to fluctuation of tap changer TC in differential circuit OF.
DT flows, but the ratio characteristic of "ratio differential request 1" is the maximum tap fluctuation differential current, as shown in FIG. 5% margin (20% considering current transformer error and differential relay error), that is, load current (low voltage side relay input terminal IR
I, )l It is a characteristic that operates when each differential current ■D of 20% for 0% and 200ch for external fault current (low voltage side relay input terminal IRI,) 1000% flows. Therefore, only one ratio differential element is output.

(c) The tap changer TC is at the minimum tap L10 position (-
15%] at 20:00 when it is healthy or when there is an external failure.

The high voltage side relay input terminal IRH is the low voltage side relay input terminal f
9.15 inches larger than RL. Differential circuit 1) +15 to F
% tap change differential current IDT is flowing, but since the ratio characteristic of ratio differential element 1 is 20%, ratio differential element 1 does not output as in (b) above (to 0) Tap changer When TC is at center position C and there is an internal failure.

As shown in Figure 5 (a), the tap fluctuation differential current fDT
is zero and 1! When the internal fault current ID flowing from the source PS to the fault point FIKi is 20% or more compared to the load current lOO%, the ratio differential element 1 outputs.

(e) The tap changer TC is at the maximum tap R10 position (+
15%) at the time of internal failure.

As shown in FIG. 5(b), when the load current is lOO%, -15% is generated in the tag fluctuation differential current II).

If the load current and the internal fault current lDy0 power factor angle are equal, the internal fault current IDy from the power supply PS will be calculated by subtracting the above differential current - 15%, 20% + 15chi = 35%, and the ratio above. Differential element 1 outputs.

(to) The tap changer TC is at the minimum tap L10 position (-
15%) at the time of internal failure.

As shown in FIG. 5, a tap fluctuation differential current IDT+15% occurs at a load current of 100%.

If the power factor angle of the load current and the internal fault current IDy are equal, the internal fault current ID from the power supply PS is 20% - 15%.
= 5% or more, the ratio differential element 1 outputs O [Problems to be solved by the invention] Since the conventional transformer protection differential relay device is configured as described above, the tap changer TC If the fluctuation of is +15%, the ratio characteristic of ratio differential element 1 is increased by 20%, taking into account the margin.
Therefore, the sensitivity to internal failures is 5%, 20%, 35% as shown in (e), (e) above.
There have been problems such as fluctuations depending on the position of the tap changer TC, low sensitivity, and insufficient detection of minor failures.

This invention has been made for a long time to solve the above-mentioned problems, and it provides a highly sensitive transformer protection differential that has constant sensitivity regardless of the position of the tap changer TC and enables the detection of minor faults. The purpose is to obtain a dynamic relay device.

[Means for solving problems] A transformer protection differential relay device according to the present invention.

Connect a current transformer to the primary and secondary sides of the protected transformer,
A group of auxiliary contacts of the primary tag switch of the protected transformer and a current converter whose output is controlled by this group of auxiliary contacts are connected to this primary current transformer, and A ratio differential element is provided that responds to the output of this current converter and the secondary current of the current transformer on the secondary side.

[Effect]

The auxiliary contact group in this invention controls the current converter in accordance with the tap movement when the tap changer moves one tap from the center position to the high voltage side and the number of relay input terminals on the high voltage side increases, This current converter reduces the high voltage side of the relay input terminal to the ratio differential element and acts to suppress the generation of differential currents due to tap switching.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The entire drawings of an embodiment of the present invention will be described below. @1
In the figure, TC-AUX is a tap changer auxiliary contact group that is linked to the movement of the main contact of the tap changer TC, and includes auxiliary contacts AC, ARl, AR2, . . . ARI O, ALl,
AL2,...AI, 1G are main contacts C, R1 respectively
,R2,...at O,Ll,I,2゜...Llo
It corresponds to Also, like the tap changer TCO main contacts, the movement between each contact is a tap contact that does not open the circuit. 2 is the compensation current transformer ACT and the high voltage side suppression circuit RCH
For example, a current converter is inserted between the tap changer T and has its output controlled by the auxiliary contact group TC-AUX.
If the l tap of C is in 1.5% steps, the output of the current converter is also configured to change in 1.5% steps. High voltage suppression circuit RCH using the output current of current converter 2
The output of the low voltage side suppression circuit RCL and the differential circuit 1) F
The output of is input to the ratio differential element 1.

FIG. 2 is a ratio differential characteristic diagram of the differential relay 10 of the present invention.
The ratio characteristic of the ratio differential element 1 is 1.5% of 1 tap of the tap changer TC, plus 5% margin (considering the error of the current transformer and the error of the differential relay), f, plus 6.5chi, i.e. Load current (low voltage side current IRL) l 6.5% for O0%, t,
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 IRI) of 1000%.

Next, the operation of this transformer mining differential relay device will be explained.

(a) When the on-load tap changer TC is at the center position C and is healthy or when the external number is 111Fo.

In this case, the main contact of the tap changer TC and the auxiliary contact TC-AUX of the tap changer are switched synchronously, so the high voltage side relay current IRIII and the low voltage side relay current I
RL are equal and the differential current is zero.

(b) Tap changer TC has RI +1.5% and is healthy or external failure occurs at 20:00.

When the tap changer TO moves from the center position C to RI,
Only during the time when the main contacts, tap changer auxiliary contacts, and TC-AUX are slightly out of synchronization (maximum 100 ms), a tap fluctuation differential current (-1DT) of 1.5% occurs, but the ratio differential element 1 Since the ratio characteristic of is 6.5% as shown in FIG. 2, the ratio differential element 1 does not output.

When the synchronization time tl- elapses, the tap fluctuation differential current (
-1DT) returns to zero.

(c) When the tap changer TC is L f -1.5% and F 0 when it is healthy or there is an external failure.

When the tap changer TC moves LIK from the center position tc,
A 5-tap fluctuation differential current (+IDT) of 1.5% occurs only during a slight synchronization difference between the main contact and the tap changer auxiliary contact TC-AUX (maximum 100m5), but the ratio characteristic of ratio differential element 1 is 6.5%, so the ratio differential element 1
No output.

After the synchronization time has elapsed, the tap fluctuation differential current (+I
D, ) returns to zero.

2) When the tap changer TC is in intermediate position C and there is an internal failure FI.

The differential current with the tap changer TC position is zero.

Internal fault current IDF flowing from power supply PS to fault point FI
However, the ratio differential element 1 outputs 6.5 times higher than the load current of 100 cm.

(E) When the tap changer TC is in a position other than center position C and there is an internal failure FI.

As mentioned in (b) and (c) above, when the tap changer TC moves, the main contact and the auxiliary contact group TC- of the tap changer TC
Only the AUX synchronization time (maximum 100 ms)
A maximum T of ±1.51 t- is generated due to the tap fluctuation differential current.

Therefore, if the power factor steel of the load current and the internal fault current IDy are equal, the internal fault current ID is 6.5 ± 1.5 = 5%.
~8 inches or more, the ratio differential element 1 outputs.

In conventional differential relays, if the variation range of the tap changer TC was ±15 degrees, the detection sensitivity of the internal fault current IDy was 5% to 35%, but it is clear from the explanation in E above that As described above, according to the present invention, a differential relay with a high sensitivity of 5 to 8% and a uniform sensitivity can be obtained, making it possible to detect slight faults in a transformer.

In the above explanation, the output change step of the current converter 2 is set to 1.5%, which is equal to the tap interval of the tap changer TC. If the output change step of the current converter 2 is 1, for example 3, the contacts of the auxiliary contact group TC-AUX of the tap changer TC are AC, AR2, AR4, .
...ARI O.

Only AL2, AL4, . . . ALlG are used, and the ratio characteristic of the ratio differential element 1 is 3% + 5% (margin) = 8chi. Further, in the above embodiment, the protected transformer MTR is 2
Although the case of a wire-wound transformer has been described, the present invention is similarly applicable to a case of a three-winding transformer.

FIG. 3 shows this embodiment. According to this,
The current transformer CTM is installed at the medium voltage terminal of the transformer, and the current transformer CT
An intermediate voltage side suppression circuit RC is connected to M, and the same effect as described above is achieved.

〔Effect of the invention〕

As described above, according to the present invention, the auxiliary contact group TC-AUXK of the tap changer TC moves to the main contact of the tap changer TC to control the magnitude of the flow IRH of the high voltage side relay 1, Since the structure is configured to remove the differential current caused by switching taps, the sensitivity is not affected by positional fluctuations of the tap changer TC, and the differential relay can be easily constructed with high sensitivity and capable of detecting small faults in the transformer. It has the effect of getting something.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of a transformer protection differential relay device according to an embodiment of the present invention, Fig. 2 is a ratio differential characteristic diagram according to the invention, and Fig. 3 is a transformer according to another embodiment of the invention. A connection diagram of a protective differential relay device, Fig. 4 is a connection diagram of a conventional transformer protection differential relay device, Fig. 5 is a diagram explaining the conventional internal fault detection sensitivity, and Fig. 6 is a conventional ratio. It is a differential characteristic diagram. MTR is the protected transformer, c'rH, c'rM, c'rL
is a current transformer, λCT is a compensation current transformer, TC-AUX is a control circuit, DF is a differential circuit, 1 is a ratio differential element, 2 is a current conversion circuit, and 10 is a differential relay. In Figure 1, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Corporation DF: 1! '+1i-10:1t61Jt-Figure 3

Claims (1)

[Claims] A protected transformer with a tap changer connected to the primary side, a current transformer connected to the primary and secondary sides of this protected transformer, and a current connected to the current transformer on the primary side. a converter, a group of auxiliary contacts that select the value of the current converted by the current converter while switching in synchronization with the switching operation of the tap changer, and an output of the current converter and current transformation on the secondary side. A transformer protection differential relay device comprising a ratio differential element responsive to the magnitude of the output current of the transformer.