What is PIR contact in circuit breaker?

Preinsertion resistor (PIR) contacts are mainly used at higher voltages (362 kV and above). The main purpose of PIR contacts is to limit the transients on the network when reconnecting lines with no load. They are only used during close and are connected in parallel with the main contacts.

What is CSD in circuit breaker?

Controlled Switching Device (CSD) is considered to be the replacement of Pre-Insertion Resistor (PIR). Moreover, tie Circuit Breaker (CB) used in One-and-a-Half-Breaker (OHB) scheme as well as in line connected with non-switchable reactor scheme are employed with PIR and CSD.

What is a pre-insertion transformer?

When a transformer is energised it may draw a large transient current from the supply connection point. Due to this, it has been common practice to install a Pre-insertion Resistor (PIR), that is placed in the circuit during the transformer energisation to reduce the inrush current and thus voltage dip.

Why closing resistor is used in a circuit breaker?

In high voltage circuit breaker closing resistor switch is used to overcome the problem of transient current and also to restrict the damage of equipment which are placed in line. Very high resistance is placed in the circuit to restrict flow of transient current.

Why is a capacitor used in a circuit breaker?

Grading capacitors are mounted on the breaker in order to prevent any contact from being exposed to excess voltage.

What is PSD relay?

This device is known as phase synchronizing device, in short PSD. Sometimes it is also referred as controlled switching device or CSD. During faulty tripping, the trip signal to the circuit breaker is directly sent from the protection relay assembly, bypassing the device.

What is controllable switch?

(1) In electrical engineering, a manual switch with two or more positions for closing and opening electrical control circuits. electronic switching unit that controls the operation of the integrating (operational) amplifiers. …

What are closing resistors?

The closing resistors are inserted using the same operating mechanism that opens and closes the main contacts. The closing resistors are in the circuit for 5-15 ms. The main contacts then shunt the current by the resistor.

Why is SF6 electronegative?

SF6 has high affinity for electrons. When a free electron comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed. This is called as electro negativity of SF6 gas.

Why Sulphur hexafluoride is called electronegative gas?

SF6 gas is highly electronegative. Due to high electronegativity, it absorbs free electrons which are produced due to arcing between contacts of circuit breaker. Combination of free electrons with molecules produces heavy and big ions, which have very low mobility.