What letter is used to indicate the relay in electric
The meaning of the double-acting relay is actually the same as that of the intermediate relay. Generally, it uses a fast intermediate relay. The main function is to electrically isolate the two circuits and to provide more contact capacity.
1. Each action of our 500KV line protection, such as phase A trip, has only two open contacts, but obviously this is not enough, so we have an open contact to go directly to the trip circuit, this other contact It is used to switch on a phase A trip relay. This relay will close 3 pairs of contacts. Contact 1 turns on phase A recloser. Contact 2 is used to alarm phase A trip, and contact 3 is used to start fault recording. Wave device. If there is no A-phase tripping relay, then the A-phase tripping with only two pairs of contacts is obviously not enough for the above purpose, so the relay here mainly expands the contacts.
2. For non-electricity protection of transformers, in order to improve reliability, do not let non-electricity relays such as gas relays directly connect to the trip circuit.
Therefore, after the non-electrical protection contact (such as a gas relay or a temperature contact) is closed, it is necessary to start the corresponding double-acting relay.
The body weight gas, on-load gas, pressure release, high oil temperature, cold control power failure repetitive relays output two pairs of contacts respectively, and once they are connected, the trip relay is activated.
The second output is used for event recording and signaling. The light gas on the body and the loaded light gas output a pair of contacts for event recording and signaling after re-activation.
About PT parallel, voltage switching and its double acting relay
PT is equivalent to a small transformer. When the secondary side, that is, the low-voltage side, needs to be paralleled, the high-voltage side must be paralleled (closed). In high-voltage equipment (110, 35, 10kV), circuit breakers are used for closing and paralleling, and intermediate relays, or voltage (PT) parallel relays, are used for secondary circuits. The coil circuit of this relay must be connected with a high-voltage busbar. Auxiliary contacts for switches and busbar cutters. why? It is to prevent the high voltage from being closed and the low voltage to be side by side. The term is electromagnetic closing. Compared with the busbar or the relay in this circuit, the parallel relay is a double acting relay, that is, the auxiliary contact must be connected before it can operate. This is a parallel relay.
In the voltage circuit, IPT and IIPT are necessary. If the PT is directly connected to the AC small bus directly, it is also unreliable, and the PT's reverse charging is prone to occur, that is, low-voltage to high-voltage charging. In order to be reliable, a group of contacts is connected to the incoming line of the small voltage bus. This contact must follow the action of the auxiliary contact of the PT high-voltage knife switch. To provide this contact, a relay is required. This relay is a PT relay. In fact, we are connecting the auxiliary contact of the PT high voltage side knife brake in the coil circuit of the PT double action relay. It may be because some of the auxiliary contacts of the knife brake are not reliable (gluing).
To sum up, in the real secondary voltage circuit, the I small bus line is the contact of the IPT double action relay, the II small bus line is the contact of the IIPT double action relay, and the two small buses are connected in the middle by the PT parallel relay. Contact. If PT is parallel, the PT parallel relay must be activated. If it is to be activated, the busbar must be operated. If the voltage bus is to be powered, the PI relay relay must be activated.
Voltage switching is much simpler. We connect the IPT power supply to the voltage source access point of a device through a group of relay contacts; the IIPT also needs to be connected through the contacts of another group of relays. Note that the connected power point is a That is to say, they are screwed together without using parallel relays. These two groups of relays are voltage switching relays. In order to make them operate reliably, especially they can't really “parallel”, so use a double coil relay, normally open contact of the knife gate to start, normally closed contact to return, anyway, don't make a mistake. Just fine. By the way, this voltage switching relay is reactivated according to the knife switch of the primary equipment of the device you want to connect. For example, if your transformer is connected to the I bus, its I knife must be closed, then the I-relay relay will be activated, and the IPT voltage will be connected to the power supply through the I-relay relay contact. Similarly, when the main transformer is connected to the II bus, the IIPT voltage is connected.
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