JPH0546776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transformer protection differential relay device for protecting a transformer that is capable of tap switching during load.

[Conventional technology]

Figure 4 is a connection diagram showing a conventional transformer protection differential relay device. In the figure, PS is the power supply of the power system, MTR is the protected transformer, TC is the on-load tap changer, and R ₁ , R ₂ ,... _R10 ,C, _L1 , _L2 ,... _L10 are the tap positions, for example, the maximum tap _R10 is +15
%, the minimum tap L ₁₀ is -15%, with 1 tap being a 1.5% step. CT _H is the transformer high voltage side current transformer, CT _L
is the low voltage side current transformer, N _H is the current transformation ratio of the high voltage side current transformer CT _H , N _L is the current transformation ratio of the low voltage side current transformer CT _L , and 10 is the differential relay (hereinafter simply referred to as differential relay). ), _R.C.H.
is the high voltage side suppression circuit, RC _L is the low voltage side suppression circuit, DF
is the differential circuit, 1 is the ratio differential element, V _H is the high voltage side voltage, V _L is the low voltage side voltage, I _1H is the high voltage side primary current, I _1L
is the low voltage side primary current, I _2H is the high voltage side secondary current, I _RH is the high voltage side relay input current, I _RL is the low voltage side relay input current, I _DT is the tap fluctuation differential current, I _DF is the internal fault current, ACT is a compensation current transformer with the number of turns n ₁ on the primary side and n ₂ on the secondary side, and when the on-load tap changer TC is at the center position C, the high voltage side relay input current I _RH and the low voltage side relay input current I _RL Convert the high-voltage side secondary current I _2H to I _RH so that they are equal. FO is the external failure point and FI is the 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.

(b) On-load tap changer (hereinafter simply referred to as tap changer) When TC is at center position C and in good condition or due to external failure
When FO.

The current transformation ratio of the compensation current transformer ACT is set to n ₁ /n ₂ = V _H・N _H /V _L・N _L so that the high voltage side relay input current I _RH and the low voltage side relay input current I _RL are equal. Therefore, if the slight error of the current transformer is ignored, the differential current of the differential circuit DF will vary even when the load current (low-voltage side relay input current I _RL ) is 100%, and even when the external fault current (low-voltage side relay input current I RL ) Even when the relay input current I _RL ) is 1000%, each is zero.

(b) The tap changer TC is at the maximum tap R10 position (+15%) when it is healthy or when there is an external failure FO.

The high voltage side relay input current I _RH is 15% smaller than the low voltage side relay input current I _RL , and the differential circuit DF
A -15% tap fluctuation differential current _IDT flows due to the fluctuation of the tap changer TC, but the ratio characteristic of the ratio differential element 1 is such that the maximum tap fluctuation differential current _IDT reaches 15% as shown in Figure 6. , 20% with a margin of 5% (considering current transformer error and differential relay error),
In other words, load current (low voltage side relay input current I _RL )
20% for 100% and 1000% for external fault current (low voltage side relay input current I _RL )
Since it has a characteristic that it operates when each differential current I _D of 200% flows, the ratio differential element 1 does not output.

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

The high voltage side relay input current I _RH is 15% larger than the low voltage side relay input current I _RL , and the differential circuit DF
A +15% tap-fluctuation differential current _IDT is flowing through, but since the ratio characteristic of the ratio differential element 1 is 20%, the ratio differential element 1 does not output as in (b) above.

(d) When the tap changer TC is in the center position C and there is an internal failure.

As shown in Figure 5A, tap fluctuation differential current
I _DT is zero, and when the internal fault current I _DF flowing from the power supply PS to the fault point FI is 20% or more compared to 100% of the load current, the ratio differential element 1 outputs.

(E) Internal failure occurs when the tap changer TC is at the maximum tap R10 position (+15%).

As _{shown in} FIG. The internal fault current I _DF from
Subtract the above differential current -15%, 20% + 15% =
At 35% or more, ratio differential element 1 outputs.

(f) Internal failure occurs when the tap changer TC is at the minimum tap L10 position (-15%).

As shown _in FIG _. The internal fault current I _DF of
20%-15%=5% or more, the ratio differential element 1 outputs.

[Problem that the invention seeks to solve]

The conventional transformer protection differential relay device is configured as described above, so if the fluctuation of the tap changer TC is ±15%, the ratio characteristic of the ratio differential element 1 is adjusted to 20%, taking into account the margin. % or more, therefore,
The sensitivity to internal failures varies depending on the position of the tap changer TC, as shown in (d), (e), and (f) above, varying from 5%, 20%, and 35%, and the sensitivity is low, making it difficult to detect slight failures. There were problems such as not being enough.

This invention was made 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 allows detection of minor faults. The purpose is to obtain a dynamic relay device.

[Means for solving problems]

The transformer protection differential relay device according to the present invention includes:
A current transformer is connected to the primary and secondary sides of the protected transformer, and the auxiliary contacts of the primary side tap changer of the protected transformer and this A current converter whose output is controlled by an auxiliary contact group is connected thereto, and a ratio differential element is provided which 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 relay input current on the high voltage side increases, This current converter serves to reduce the high-voltage relay input current to the ratio differential element and to suppress the generation of differential current due to tap switching.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, TC-AUX is a tap switch
A tap changer auxiliary contact group that is linked to the movement of the TC main contact, auxiliary contacts AC, AR1, AR2,...AR
10, AL1, AL2, ...AL10 are the main contacts C, R1, R2, ...R10, L1, L2, ...L, respectively
It corresponds to 10. Also, like the main contacts of the tap changer TC, the movement between each contact is a tap contact that does not open the circuit. 2 is compensation current transformer ACT
A current converter is inserted between the high voltage side suppression circuit RC _H and the output is controlled by the auxiliary contact group TC-AUX.
If the step is 1.5%, the output of the current converter is also 1.5
It is configured to change in % steps. The output of the high voltage suppression circuit _RCH , the output of the low voltage side suppression circuit _RCL , and the output of the differential circuit DF based on the output current of the current converter 2 are input to the ratio differential element 1.

FIG. 2 is a ratio differential characteristic diagram of the differential relay 10 of the present invention. 6.5% including differential relay error)
In other words, for 100% of the load current (low voltage side current I _RL )
6.5%, also external fault current (low voltage side current I _RL )
The characteristic is that it operates when a differential current I _D of 65% compared to 1000% flows.

Next, the operation of this transformer protection 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 there is an external failure FO.

In this case, the main contacts of the tap changer TC and
Since the tap changer auxiliary contacts TC-AUX each switch synchronously, the high voltage side relay current I _RH and the low voltage side relay current I _RL are equal, and the differential current is zero.

(b) Tap changer TC is RI + 1.5% when it is healthy or when there is an external failure FO.

When the tap changer TC moves from center position C to RI, the main contact and the tap changer auxiliary contact TC
-Aux slight synchronization time (maximum approx. 100m)
s), the tap variation differential current (-I _DT ) is 1.5
%, but the ratio characteristics of ratio differential element 1 are:
As shown in FIG. 2, it is 6.5%, so the ratio differential element 1 does not output.

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

(c) Tap changer TC is LI - 1.5% when it is healthy or when there is an external failure FO.

When the tap changer TC moves from center position C to LI, the main contact and the tap changer auxiliary contact TC-
AUX slight synchronization time (maximum approx. 100m)
s) only, the tap fluctuation differential current (+I _DT ) is 1.5
% occurs, but the ratio characteristic of ratio differential element 1 is
Since it is 6.5%, the ratio differential element 1 does not output.

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

(d) Tap changer TC is in intermediate position C and internal failure occurs.
At FI time.

The differential current associated with the tap changer TC position is zero, and the internal fault current I _DF flowing from the power supply PS to the fault point FI is 6.5% or more compared to 100% of the load current,
Ratio differential element 1 outputs.

(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, the tap changer TC
When moving the main contact and the auxiliary contact group TC-AUX of the tap changer TC, the synchronization time (maximum approx. 100
ms), the tap fluctuation differential current I _DT is up to ±
1.5%.

Therefore, if the power factor angles of the load current and internal fault current I _DF are equal, then the internal fault current I _DF is 6.5±1.5
= 5% to 8% or more, the ratio differential element 1 outputs.

In conventional differential relays, tap switch
If the variation range of TC was ±15%, the detection sensitivity of internal fault current _IDF was 5% to 35%, but as is clear from the explanations (d) and (e) above, the present invention According to the method, a differential relay with high sensitivity of 5 to 8% and uniform sensitivity can be obtained, and it is 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, but it is not limited to this and can be configured as desired. , when the output change step of the current converter 2 is set to 3%, for example, the auxiliary contact group TC-AUX of the tap changer TC
The contacts are AC, AR2, AR4,...AR10, AL
2, AL4, . . . AL10 are used, and the ratio characteristic of the ratio differential element 1 is 3% + 5% (margin) = 8%. In addition, in the above embodiment, the protected transformer MTR
Although the case of a two-winding transformer has been described, the same applies to a three-winding transformer.

FIG. 3 shows this embodiment. According to this, the current transformer C _M is installed at the medium voltage terminal of the transformer, the medium voltage side suppression circuit R _M is connected to the current transformer C _M , and the same effect as described above is achieved.

〔Effect of the invention〕

As described above, according to the present invention, the magnitude of the high voltage side relay input current I _RH is controlled in conjunction with the main contact of the tap changer TC by the auxiliary contact group TC-AUX of the tap changer TC. Since the structure is configured to remove the differential current caused by the switching of the 1. current tap, the secondary side of the current transformer is not opened even momentarily when the current tap is switched, such as the protection device shown in Japanese Patent Application Laid-Open No. 60-5731. Consideration will be given to ensure that this does not occur.

2. It is necessary that one of the tap switching auxiliary contacts A'B'C' is always closed, and a special tap switching auxiliary contact is required.

3. If the secondary side of the current transformer becomes open due to poor contact with the tap changer when switching the current tap, abnormal voltage will occur because the excitation impedance of the current transformer is extremely large, resulting in danger or burnout of the current transformer. There is a risk of

This has the effect of providing a simple differential relay that does not cause such inconveniences, has sensitivity that is not affected by positional fluctuations of the tap changer TC, and is highly sensitive and capable of detecting minor faults in the transformer. .

[Brief explanation of the drawing]

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, and Fig. 5 is a connection diagram of a conventional transformer protection differential relay device.
Figure 6 is a diagram explaining conventional internal fault detection sensitivity.
The figure is a conventional ratio differential characteristic diagram. MTR is the protected transformer, CT _H , CT _M , CT _L are the current transformers, ACT is the compensation current transformer, TC-AUX is the tap changer auxiliary contact group, R _H , RC _M , R _L are the control circuits, DF is a differential circuit, 1 is a ratio differential element, 2 is a current conversion circuit, and 10 is a differential relay. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A protected transformer with a tap changer connected to its primary side, a current transformer connected to the primary and secondary sides of this protected transformer, and the current connected to the current transformer on the primary side. a converter, a group of auxiliary contacts that select the current value converted by the current converter while switching in synchronization with the switching operation of the tap changer, and a group of auxiliary contacts that select the current value converted by the current converter, and the output of the current converter and the current transformer on the secondary side. A transformer protection differential relay device comprising a ratio differential element responsive to the magnitude of the output current.