JPH10341527A - Transformer protective relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a protective relay surely against an assumed trouble and protect instruments in a circuit, by dividedly disposing a combination of a current transformer and the protective relay according to a purpose of protection. SOLUTION: A transformer protective relay device is provided with the first high voltage side current transformer 2 and a lower voltage side current transformer 3 which are formed respectively at the high voltage side and the low voltage side of a transformer 1 to be protected, a rate differential relay 5 which is operated by the output of both the current transformers 2, 3, the second high voltage side current transformer 7 which is formed at the high voltage side of the transformer 1 to be protected, and an overcorrect relay 9 which is operated by the output of the second high voltage side current transformer 7, whereas the rate of current transformation is set so as to be a value which meets the rated current of the transformer 1 to be protected in the first high voltage side current transformer 2 and the low voltage side current transformer 3, and the rate of current transformation is set large in the second high voltage side current transformer 7 so that the current transformer may not cause magnetic saturation at the time of overcorrect inflow of the transformer 1 to be protected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to protection of a starting transformer directly connected to an electric power system, by appropriately selecting a current ratio of a current transformer for a protective relay against an assumed accident. The present invention relates to a protective relay device for surely protecting a device.

[0002]

2. Description of the Related Art Generally, protection of a transformer is performed by monitoring a difference between current ratios detected by current transformers installed on the high voltage side and the low voltage side of the transformer, respectively, and surrounding the high voltage side and the low voltage side current transformer. A differential relay that operates for a short-circuit fault within the specified range, and an overcurrent relay that operates for a short-circuit fault in the entire circuit below the high-side current transformer by monitoring the current detected by the high-side current transformer It is composed of Here, the overcurrent relay plays a role of back-up protection of the ratio differential relay. FIG. 4 is a single-line diagram showing a conventional transformer protection relay device.
1 is a transformer, 2 is a high voltage side current transformer, 3 is a low voltage side current transformer, 4
Is an overcurrent relay, 5 is a ratio differential relay, and 6 is a transformer high voltage side breaker.

Next, the operation will be described. In FIG. 4, A is a three-phase short circuit fault point on the high voltage side of the transformer, and is hereinafter referred to as a point A fault. Conventionally, a transformer protection relay has a high-voltage side current transformer 2 for detecting a current together with an improvement in the sensitivity of a ratio differential relay 5 in order to improve the detection sensitivity to a micro accident such as an interlayer short circuit inside the transformer 1. And the current ratio of the low voltage side current transformer 3 is selected to a value corresponding to the rated current of the transformer 1 to improve the sensitivity of the detected current. The overcurrent relay 4 operates by detecting an overcurrent when the ratio differential relay 5 is inoperative. Furthermore,
This device protects against the micro-accident in the transformer as well as the A-point accident.

[0004]

Since the conventional transformer protection relay device is constructed as described above, a small accident inside the transformer can be protected without any problem. If an excessive current flows from the high-voltage side, the high-voltage side current transformer becomes magnetically saturated, and it becomes difficult to detect a fault current, which may lead to a situation where the transformer cannot be protected. The degree of magnetic saturation of the current transformer due to an excessive fault current is a characteristic of the current detection circuit uniquely determined from the current transformer ratio, the rated load, the overcurrent constant, and the actual load. As a countermeasure against current transformer magnetic saturation, there is a means to adopt a current transformer with transient characteristics, but it is expensive, the external dimensions are large, and it is difficult to install it as a bushing current transformer for circuit breakers and transformers Therefore, adoption has not progressed, and no effective countermeasures have been taken.

[0005] The protection relay device according to the present invention is divided into protection for detecting a micro accident inside the transformer and protection in consideration of magnetic saturation of the current transformer when an excessive current flows, and is installed according to the purpose of protection. It was done.

[0006]

A transformer protection relay according to the present invention comprises a first high-side current transformer and a low-side current transformer provided respectively on a high voltage side and a low voltage side of a protected transformer. A ratio differential relay operated by the outputs of the two current transformers, a second high voltage side current transformer provided on the high voltage side of the protected transformer,
An overcurrent relay operated by an output of the second high-side current transformer, wherein the first high-side current transformer and the low-side current transformer have a current ratio that is equal to a rated current of the protected transformer. The second high voltage side current transformer is set to a suitable value, and the current transformer ratio is set large so that the current transformer does not cause magnetic saturation when an excessive current flows into the protected transformer. .

Further, in the above configuration, an overcurrent relay operated by the output of the first high-voltage side current transformer is added.

A first high-side current transformer and a low-side current transformer provided on the high-voltage side and the low-voltage side of the protected transformer, respectively;
A ratio differential relay operated by the outputs of the two current transformers, second high-voltage side current transformers and low-voltage side current transformers provided on the high and low voltage sides of the protected transformer, respectively. Ratio differential relay operated by the output of the relay, the time-limited overcurrent relay operated by the output of the first high-voltage current transformer, and the instantaneous overcurrent operated by the output of the second high-voltage current transformer A relay, wherein the first high-side current transformer and the first low-side current transformer set a current ratio to a value corresponding to a rated current of the protected transformer, and The high-voltage side current transformer has a large current transformer ratio set so that the current transformer does not cause magnetic saturation when an excessive current flows into the protected transformer.

Further, the operation of the first ratio differential relay is stopped (locked) for a predetermined time immediately after the transformer power supply circuit breaker is closed.
I am trying to do it.

In addition, protection coordination is performed so that the instantaneous overcurrent relay operates at a larger current than the time-limited overcurrent relay.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. In FIG. 1, 1 is a protected transformer,
2 is a high voltage side current transformer whose current ratio is selected to a value corresponding to the high voltage side rated current of the transformer, 3 is a low voltage side current transformer whose current ratio is selected to a value corresponding to the low voltage side rated current of the transformer, 4 is a time limiting type overcurrent relay for transformer protection (with instantaneous element), 5 is a ratio differential relay for transformer protection, 6 is a high voltage side circuit breaker for transformer, and 7 is an overcurrent in case of point A accident. The transformer high-voltage side current transformer having a large current transformer ratio in consideration of magnetic saturation, 8 is a current transformer having a current transformer ratio selected from the current transformer ratio of the current transformer 7 in setting the ratio differential relay 10. And 9, a momentary overcurrent relay for protecting circuits below the transformer high-side circuit breaker, and 10 a ratio differential relay for protecting circuits from the transformer high-side circuit breaker to the transformer.

Next, the operation will be described. In FIG. 1, regarding a small short circuit accident inside the transformer 1, the current ratio is selected to a value corresponding to the rated current of the transformer, and the high voltage side current transformer 2 having improved current detection sensitivity and the low voltage side The ratio differential relay 5 operates according to the ratio difference between the detection currents of the current transformers 3 to perform transformer protection. When the ratio differential relay 5 is inoperative, protection is provided by a time limit type overcurrent relay (with an instantaneous element) 4 as a post-protection protection.

In the case of the point A accident, the excessive current inflow from the power supply side causes the high voltage side current transformer 2 to reach magnetic saturation, and the ratio differential relay 5 which is a protection relay connected thereto and the time limit type overcurrent relay (instantaneous) Element 4) is likely to be inoperative. At this time, the high-voltage side current transformer 7 selecting a current ratio in consideration of the magnetic saturation of the current transformer normally detects the fault current without magnetic saturation, and the ratio differential relay which is a protection relay connected to the fault current. 10 or the instantaneous overcurrent relay 9 operates to protect the circuit.

The reason why the overcurrent relays are selectively used as the protection of the ratio differential relays 5 and 10 between the counter-time-type overcurrent relay (with an instantaneous element) 4 and the instantaneous overcurrent relay 9 is to consider protection coordination between each other. Thus, the instantaneous overcurrent relay 9 operates with a current larger than that of the instantaneous element of the overtime relay 4 (with instantaneous element).

In the above description, the current transformer ratio is increased in consideration of magnetic saturation at the time of inflow of excessive current into the transformer high voltage side current transformer 7, but the tolerance of magnetic saturation for overcurrent of the current transformer is naturally changed. Since the current ratio is proportional to the rated load and the overcurrent constant, the current ratio to be selected differs depending on the relationship between the rated load and the overcurrent constant. In particular, a transformer that directly connects equipment in a power plant and an electric power system has a large transformer ratio, and if the transformer current transformer ratio on the high voltage side is too large, it may be difficult to settle the ratio differential relay. In order to compensate for the limitation of the current transformer ratio in the setting of the ratio differential relay, it is also effective to increase the rated load and the overcurrent constant to improve the tolerance to magnetic saturation.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, 1 is a protected transformer, 2 is a high voltage side current transformer whose current ratio is selected to a value corresponding to the high voltage side rated current of the transformer, and 3 is a current ratio which is suitable for the low voltage side rated current of the transformer. The current transformer selected for the low voltage side, the differential relay 5 for transformer protection ratio, the high voltage circuit breaker 6 for the transformer,
Reference numeral 7 denotes a transformer high-voltage side current transformer whose current transformer ratio is increased in consideration of magnetic saturation of the current transformer when an excessive current flows in at the point A accident, and 4 denotes an anti-time overcurrent relay for protecting the transformer.

Next, the operation will be described. In FIG. 2, the starting transformer can be protected by the ratio differential relay 5 in the case of a micro short circuit accident inside the transformer as in the related art. The difference from the conventional protective relay is that the current transformer for the overcurrent relay and the current transformer for the ratio differential relay are divided.The current transformer for the overcurrent relay is The current transformer ratio is increased so as not to cause saturation. Therefore, the high-voltage side current transformer 7 normally detects the fault current without magnetic saturation due to the excessive current at the time of the point A fault, and the overcurrent relay 4 which is a protection relay connected thereto operates to protect the circuit. Can be.

In the above description, the current transformers for the ratio differential relay 5 and the overcurrent relay 4 as a back-up protection relay are divided into the high voltage side current transformers 2 and 7, but the conventional protection relay is used. As in the case of the power transmission device, another overcurrent relay may be connected to the high-voltage side current transformer 2 as a back-up protection for the ratio differential relay 5 and used in combination with the ratio differential relay 5. At this time, of course,
The current transformer 7 and the overcurrent relay 4 in consideration of magnetic saturation at the time of inflow of an excessive current are to be left, and a protection relay device in consideration of protection coordination between the added overcurrent relay and the overcurrent relay 4 is provided. .

Embodiment 3 Third Embodiment A third embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a flowchart schematically showing an interlock diagram of the operation of the ratio differential relay with respect to the single-line diagram of FIG. When the transformer 1 in FIG. 1 is excited, an exciting rush current flows for several tens of msec. However, the exciting rush current may cause the ratio differential relay 5 to malfunction. 2. Description of the Related Art Conventionally, a ratio differential relay may be provided with a mechanism for detecting a harmonic contained in an exciting inrush current and locking the operation in order to prevent a malfunction due to the inrush exciting current. However, the harmonic content of the inrush current varies variously depending on the structure of the transformer and the state of the residual magnetic flux of the transformer core at the time of excitation, and the above-mentioned operation lock is not a fundamental malfunction prevention measure.

Here, by employing the protection device of FIG. 1 and adopting the operation configuration of the flow chart of FIG. 3, the operation of the ratio differential relay 5 is locked by the on-delay timer for several tens of msec after the excitation of the transformer. Thus, malfunction can be easily prevented. However, by providing this operation lock circuit, the protection function of the ratio differential relay 5 is lost for a certain period of time, but the circuit can be protected by the ratio differential relay 10. The high-voltage side current transformer 7 with respect to the ratio differential relay 10 increases the current transformer ratio so that malfunction due to the inrush current of the excitation is reduced.

In the above description, the case where the present invention is mainly used for protecting a starting transformer directly connected to a power system has been described, but it goes without saying that the present invention can be applied to other transformers.

[0022]

As described above, according to the present invention, the protection of the current transformer by combining the protection considering the magnetic saturation of the current transformer due to the inflow of the excessive current from the power supply and the protection for detecting the micro-accident is provided. This has the effect of preventing the loss of the protection relay function due to the magnetic saturation and of building a protection device that maintains the detection sensitivity in the event of a micro short circuit accident.

Further, by providing a ratio differential relay for detecting a micro accident and a ratio differential relay for detecting an accident when an excessive current flows, more highly accurate change protection can be achieved.

Further, there is an effect that a circuit for preventing a malfunction of the protection relay due to an inrush current at the time of exciting the transformer can be easily constructed while maintaining the protection function.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a transformer protection relay device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a transformer protection relay device according to Embodiment 2 of the present invention.

FIG. 3 is a flowchart illustrating an operation of a transformer protection relay device according to Embodiment 3 of the present invention.

FIG. 4 is a block diagram showing a conventional transformer protection relay device.

[Explanation of symbols]

1 protected transformer, 2 high voltage side current transformer, 3 low voltage side current transformer, 4 time limit type overcurrent relay, 5 ratio differential relay,
6 Circuit breaker, 7 High voltage side current transformer, 8 Low voltage side current transformer, 9
Instantaneous overcurrent relay, 10 ratio differential relay, A short circuit fault point.

Claims (5)

[Claims] 1. A first high-side current transformer and a low-side current transformer respectively provided on a high-voltage side and a low-voltage side of a protected transformer, a ratio differential relay operated by outputs of the two current transformers, A second high voltage side current transformer provided on the high voltage side of the protected transformer,
An overcurrent relay operated by an output of the second high-side current transformer, wherein the first high-side current transformer and the low-side current transformer have a current ratio that is equal to a rated current of the protected transformer. The second high voltage side current transformer is set to a suitable value, and the current transformer ratio is set large so that the current transformer does not cause magnetic saturation when an excessive current flows into the protected transformer. Transformer protection relay device. 2. The transformer protection relay according to claim 1, further comprising an overcurrent relay operated by an output of the first high-voltage side current transformer. 3. A high voltage side current transformer and a low voltage side current transformer respectively provided on a high voltage side and a low voltage side of a protected transformer, and a first ratio difference operated by outputs of the two current transformers. Motion relay,
A second high-voltage current transformer and a low-voltage current transformer respectively provided on the high-voltage side and the low-voltage side of the protected transformer, a second ratio differential relay operated by the outputs of both current transformers, First
And a momentary overcurrent relay operated by the output of the second high-voltage side current transformer that operates by the output of the high-voltage side current transformer. The first low voltage side current transformer sets the current ratio to a value corresponding to the rated current of the protected transformer, and the second high voltage side current transformer sets an excessive current of the protected transformer. A transformer protection relay, wherein the current transformer ratio is set large so that the current transformer does not cause magnetic saturation when current flows. 4. The transformer protection relay according to claim 3, wherein the operation of the first ratio differential relay is stopped (locked) for a predetermined time immediately after closing the transformer power supply circuit breaker. Electrical equipment. 5. The transformer protection relay device according to claim 3, wherein protection coordination is performed so that the instantaneous overcurrent relay operates at a larger current than the anti-time limit type overcurrent relay.