JPS6130498B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a capacitor type that can distinguish between a secondary side short circuit and an abnormal increase in primary side voltage, suppress the short circuit current in the case of a secondary side short circuit, issue a secondary short circuit alarm, and issue an abnormal voltage alarm in the case of an abnormal increase in the primary side voltage. This relates to potential transformers (hereinafter referred to as PDs). It is a well-known fact that when a secondary short circuit occurs between the secondary terminals of a PD, an overcurrent flows and an abnormally high voltage is generated at the voltage dividing terminals, which is dangerous from both thermal and insulation standpoints. Therefore, it is necessary to operate a short-circuit protection device to reduce the short-circuit current at the same time as a secondary-side short-circuit accident occurs, and to issue a short-circuit alarm to quickly locate the failure location, remove the cause, and take appropriate measures. However, in general, secondary short circuit protection devices or warning devices operate by detecting an increase in secondary short circuit current, a rise in divided voltage, or in the case of a primary reactor method, a rise in voltage between the terminals of a resonant reactor. However, malfunction may occur due to other causes such as an increase in current due to an increase in the primary side voltage of the PD or an increase in voltage at various parts. In particular, the recently used AMPPD, that is, the required power is amplified by an amplifier, and the PD only supplies voltage to the input of the amplifier, and in those that do not need to supply power, the main capacitor and voltage divider are used. Because the capacitance of the capacitor is small, the conventional
Compared to PD, the increase in short-circuit current and the increase in divided voltage at the time of a secondary short circuit are considerably smaller. In such a PD, the increase in current when the voltage on the primary side of the PD rises and the degree of voltage rise at each part are not much different from those when the PD's secondary side is short-circuited. Therefore, the short-circuit protection device and alarm device are activated not only when the secondary side of the PD is short-circuited, but also when the voltage on the primary side of the PD rises abnormally, which is a problem in terms of system maintenance. In view of these points, the present invention distinguishes between a short circuit on the secondary side of the PD and an abnormal rise in the voltage on the primary side of the PD, operates a short circuit protection device in the case of a secondary short circuit, reduces the short circuit current, and also provides a short circuit alarm device. operate,
It is an object of the present invention to provide a capacitor type voltage transformer capable of operating an abnormal voltage warning device when the primary side voltage rises abnormally. An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, C1 is the main capacitor, C2
is a voltage dividing capacitor, T is a leakage transformer that has an inductance that maintains resonance with the capacitance of the main capacitor C1 and voltage dividing capacitor C2, and transforms the divided voltage into the required secondary voltage, and W1 is a voltage dividing capacitor C2. W2 is the secondary winding of the leaky transformer T connected to both ends of the leaky transformer T, W2 is the secondary winding of the leaky transformer T, WC is a coupling winding wound electromagnetically close to the primary winding W1, U, V is the primary terminal, u and v are the secondary terminals,
a, b are coupled winding terminals, RY1 is secondary terminals u, v
An abnormal voltage detection relay that is connected between the two and detects an abnormal rise in the secondary voltage induced due to an abnormal rise in the primary voltage. RY2 is the difference voltage between the induced voltage between the coupling winding WC and the secondary winding W2. A secondary short circuit detection relay is connected between one end b of the coupling winding WC and one end v of the secondary winding W2 in order to detect this, 1 and 2 are the contacts of the relay RY1, 3, 4, 5, 6 is the contact of relay RY2, A1, A2 are abnormal voltage alarm terminals, A3, A
4 is a secondary short circuit alarm terminal, R1 is a fixed burden resistance, R
2 is a short circuit current suppression resistor. In the steady state, relay RY1 and relay RY2 are set not to operate, and short-circuit current suppression resistor R2 is in a short-circuited state by contacts 3 and 4 of relay RY2, supplying power to the secondary load. On the other hand, contacts 1 and 2 of relay RY1 and contacts 5 and 6 of relay RY2 are in an open state. In this state, if a secondary short circuit accident occurs between the secondary terminals u and v, a large secondary short circuit current flows and the voltage across the primary winding W1 of the leaky transformer T rises abnormally. At this time, the voltage between the secondary terminals u and v drops to the voltage determined by the short circuit impedance on the secondary side,
Relay RY1 does not operate and relay contacts 1 and 2 remain open. On the other hand, since a voltage approximately proportional to the voltage generated across the primary winding W1 is generated in the coupling winding WC, which is electromagnetically tightly wound with the primary winding W1, the coupling winding WC and the secondary winding The voltage difference between the induced voltage and W2 becomes larger than in the steady state, and the relay
RY2 operates, contacts 3 and 4 are opened, and contacts 5 and 4 are opened.
6 is closed. As a result, the short circuit current suppression resistance R
2 is inserted into the secondary winding circuit to reduce the short-circuit current, and the contacts 5 and 6 can generate an alarm. When the short circuit current is reduced, the voltage across the coupling winding WC, which is approximately proportional to the voltage across the primary winding W1, also decreases, so the detection voltage of the relay RY2 becomes low, but the value of the short circuit current suppression resistor R2 should be adjusted appropriately. If selected, relay RY2 can be activated and short-circuit current suppression resistor R2 can be left inserted. The operation when the secondary side is short-circuited has been described above, and next, the operation when the primary side of the PD rises abnormally will be explained. At this time, the voltage across the voltage dividing capacitor C2, that is, the voltage across the primary winding W1 of the leaky transformer T increases. At this time, the induced voltages in the coupled winding WC and the secondary winding W2 also rise approximately in proportion to the voltage across the primary winding W1. Therefore the coupled winding WC
The voltage difference between the voltages induced in the secondary winding W2 and the secondary winding W2 is extremely small compared to when the secondary terminals u and v are short-circuited, and the relay RY2 does not operate in this state. However, as the voltage across the primary winding W1 rises, the voltage between the secondary terminals u and v of the secondary winding W2 rises, which causes the relay RY1 to operate, closing contacts 1 and 2. When closed, an alarm can be issued for an abnormal rise in the PD primary voltage. In any of the above cases, when the secondary short circuit state and the abnormally increased primary voltage state are released, the steady state is automatically restored, and the PD can supply power to the secondary load. The results of actual tests using this device will be described below. The PD rating is primary voltage 550/√3Kv, secondary voltage 110/√3Kv, combined winding voltage 100V, rated load 2VA, short circuit current suppression resistance 100Ω, primary voltage abnormal rise detection relay RY1 set voltage 72V, The set voltage of secondary short circuit detection relay RY2 is 83V. The result was the table below.

[Table] As shown above, in steady state, relay RY
1. Since neither relay RY2 operates, only relay RY2 operates when the secondary short circuit occurs, and only RY1 operates when the primary voltage rises abnormally, it is clear whether the fault is on the primary side or the secondary side of the PD. can be distinguished. Next, another embodiment of the present invention will be described. Figure 2 is a diagram showing an example of a circuit when the means for detecting the differential voltage is changed. C3 is a capacitor that is part of the voltage dividing capacitor C2, and parts shown with other symbols are shown with the same symbols in Figure 1. Since it is the same as the part described above, its explanation will be omitted. This is the difference voltage applied to relay RY2 to the voltage across voltage dividing capacitor C3 and secondary winding W.
Detection is made from the second induced voltage. In addition, Fig. 3 is a diagram showing an example of a circuit in a primary reactor type PD, where RL is a resonant reactor,
W3 is the secondary winding of the resonant reactor RL. Since the parts indicated by other symbols are the same as the parts indicated by the same symbols in FIG. 1, the explanation thereof will be omitted.
This is designed to detect the differential voltage applied to the relay RY2 from the secondary winding W3 and the secondary winding W2 of the resonant reactor RL. The operating principle of each of the above embodiments is the same as that of the first embodiment. By using the PD of the present invention configured as described above, an alarm can be issued by distinguishing between a short-circuit accident on the PD's secondary side and an abnormal voltage rise on the grid, that is, the primary side of the PD, and a warning can be issued in the event of a short-circuit accident on the secondary side. In some cases, the short-circuit current can be suppressed to a level that is thermally and voltage-safe for the PD. Additionally, since it identifies the location of the abnormality and issues a warning, prompt treatment and repair can be carried out, which is a major advantage in terms of system maintenance.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a capacitor type potential transformer according to the present invention, and FIGS. 2 and 3 are circuit diagrams showing other embodiments of the present invention. C1 is the main capacitor, C2 is the voltage dividing capacitor,
T is the leaky transformer, W1 is the primary winding of the leaky transformer T, W2 is the secondary winding of the leaky transformer T, WC is the coupled winding of the leaky transformer T, and W3 is the resonant reactor.
The secondary winding of RL, C3, represents a part of the voltage dividing capacitor C2.

Claims (1)

[Claims] 1. A leaky transformer with a primary winding connected to both ends of a voltage dividing capacitor, a first detector that detects the voltage of the primary winding circuit of this leaky transformer, and a voltage of the secondary winding circuit of the leaky transformer. A second detector detects a voltage difference between the first and second detectors, and if the difference voltage is larger than a predetermined value, it is determined that there is a secondary short circuit accident, and the voltage difference is determined to be a predetermined value. If it is smaller than the value, it is determined that the primary side voltage has increased abnormally, and when the secondary side short circuit accident is determined, a current suppressing device is inserted into the secondary winding circuit of the leaky transformer and an alarm device is activated. a first protection device; a second protection device connected between the secondary windings of the leaky transformer to detect an abnormal rise in secondary voltage due to an abnormal rise in the primary voltage and activate an alarm device; A capacitor-type voltage transformer equipped with a protection device.