What is cable differential protection?
What is cable differential protection?
In this cable/line design, cable differential protection provides reliable discrimination between faults in the cables and on overhead lines. They exchange current phasor information to determine if a fault is on the cable (In-Zone) or on the overhead line (Out-of-Zone).
Which relay is used in differential protection?
Voltage Balance Differential Relay For the protection of the feeders, the voltage balance differential relays are used. The voltage differential relay uses two similar current transformer places across the protective zone with the help of pilot wire.
Which CT is used for differential protection?
The PS class CTs are used for differential protection. The differential protection is also called the zone or unit protection.
What is 87l relay?
The pilot wire differential relay is a high-speed relay designed for protection of transmission and distribution lines. They are generally applied on short lines, normally less than 40 km long.
How does pilot wire protection work?
The pilot wire protection system detects and responds to phase to phase faults, phase to ground faults and phase to phase to ground faults that may occur within the protected section by detecting and responding to an excessive differential current existing between a first and a second end of the protected section.
Where is differential protection used?
Differential protection schemes are mainly used for protection against phase-to-phase fault and phase to earth faults. The differential protection used for power transformers is based on Merz-Prize circulating current principle. Such types of protection are generally used for transformers of rating exceeding 2 MVA.
What are the different types of differential relay?
There are mainly two types of differential relay depending upon the principle of operation.
- Current Balance Differential Relay.
- Voltage Balance Differential Relay.
What is special protection CT?
PS Class CT is also known as PX Class or simply Class X Current Transformer. It is special type of current transformer meant for protection purpose. You may refer Accuracy Class of CT for detail. In many protection applications, core saturation will almost occur during the transient phase of a heavy short circuit.
Why PS class CT used for differential protection?
PS Class CT – This type of ct is use for where the current balance is precisely required to be maintained. In the Overall differential protection, Transformer, Generator protection needs PS class CT. The developed voltage in ct core is less than the knee voltage of the CTs. 2.
What are the limitations of pilot wire protection scheme?
The disadvantages listed in the ” Relay Handbook” are:
- Cost of pilot wire channel.
- Cost of special current transformers.
- Necessity of uniform characteristics of current transformers.
- Lack of supervision of pilot wire circuit continuity.
- Induction in pilot wire circuit.
What are the limitations of wire pilot protection?
If there is a break in the pilot-wire circuit, the system will not operate. This system is very expensive owing to the greater length of pilot wires required. In case of long lines, charging current due to pilot-wire capacitance effects may be sufficient to cause relay operation even under normal conditions.
