Table of Contents
What is out of step relaying?
OUT-OF-STEP PROTECTION PHILOSOPHY The philosophy of out-of-step relaying is simple and straightforward: avoid tripping of any power system element during stable swings. Protect the power system during unstable or out-of-step conditions.
What is out of step condition?
Out of step (OOS) is considered an abnormal condition in power system. At this case, the electrical power is not equalized with the mechanical power for the generator. So, OOS leads to variation in three-phase voltage and current for the power system.
What is out of step in power system?
Out-of-Step or Loss of Synchronism is a condition where a generator experiences a large increase in the angular difference of the Electro Motive Force (EMF) with other generators or portions of a system to which it is connected, usually following a major power system disturbance.
What is a distance relay 21?
The goal of a distance relay (ANSI/IEEE code 21) is to trip its circuit breaker(s) if a fault occurs within its programmed “reach” and to ignore both normal operating loads and faults lying outside its reach.
What is pole slip protection?
Pole slipping protection, also referred to as loss of synchronism protection, is required when a generator loses synchronism with the utility’s main source of power and is subjected to high fluctuations in the current passing through it.
What is stable power swing?
A power swing is stable when, following a disturbance, the rotation speed of all machines returns to synchronous speed. A power swing is unstable when, following a disturbance, one or more machines do not return to synchronous speed, thereby losing synchronism with the rest of the system.
What is the power swing?
Power swing is a variation in three-phrase power flow which occurs when the generator angles are advancing or retarding relative to each other in response to changes in load magnitudes and direction, line switching, loss of generation, faults, and other system disturbance.
What causes power swing?
Abstract—Power Swing which is basically caused by the large disturbances in the power system which if not blocked could cause wrong operation of the distance relay and can generates wrong or undesired tripping of the transmission line circuit breaker.
What is power swing blocking?
A power-swing blocking (PSB) function is available in modern distance relays to prevent unwanted distance relay element operation during power swings. The main purpose of the PSB function is to differentiate between faults and power swings and block distance or other relay elements from operating during a power swing.
What is generator slip?
The motor normally turns slightly slower than the synchronous speed; the difference between synchronous and operating speed is called “slip” and is usually expressed as per cent of the synchronous speed. For example, a motor operating at 1450 RPM that has a synchronous speed of 1500 RPM is running at a slip of +3.3%.
What is field suppression of alternator?
Field Suppression It is a method of discharging stored energy in the field through a resistor. • Whenever a fault occurs in the alternator winding, its C.B is tripped. • But fault remains there since the voltage is induced in the generator with the help of field.
How can I improve my power stability?
Detailed Solution
- Increasing the system voltage.
- Increase in the X/R ratio.
- Using high-speed governors on machines.
- faster fault clearing.
- High-speed circuit breakers help to clear the fault as quickly as possible.
- By turbine fast valving.
- High-speed excitation.
- Use of auto re-closing breakers.
What is transfer reactance?
Transfer reactance(x): The total reactance X between two voltage sources V and E is called the transfer reactance. The maximum power limit is inversely proportional to the transfer reactance.
What is PSB relay?
Which relay is most affected by power swing?
A reactance relay is suitable for the protection of a short transmission line because its operation is independent of arc resistance. The relay which is selected for a long transmission line should be less affected due to power swings. Hence Mho relay is preferred.
How do you find a power swing?
In [20], power swings are detected based on the rate of changes in the RMS values of current during faults and power swings. Although this method is capable of detecting high impedance faults during power swings, it cannot detect asymmetrical one-phase power swings induced by single-pole switching.
What is Sotf relay?
Switch onto fault (SOTF) trip logic provides a window of time for the enabling of nondirectional relay elements and instantaneous overreaching directional elements after the circuit breaker closes to energize a line.
Is out-of-step relay testing valid for symmetrical fault detection during power swing?
Sauhats et al. [89] presented out-of-step relay testing procedure for distance relays, but the same is not validated for symmetrical fault detection during power swing involving high electrical resistance.
How does the impedance relay work in a circuit?
At a nearby fault, the impedance relay will operate and its output relay picks up. If, after fault clearing, there will be a swing only, the impedance will pass out of the oval on the same side of the X-axis as it entered.
What is the difference between the measuring relay 7432 and 1371?
The measuring relay drawing 7432 010S-ÄB. relay is up a switch a dc/ dc auxiliary a static supply i 125), an impcdanee measurim; RXzF aux. relays for tripping The tripping relay (1371 is Of type RXME 1B flag heavy-duty