Differential Relay Working Pdf

Saturation detector sat with many differential protection systems relay instability may cause to trip if the main current transformers saturate.

Differential relay working pdf.

The high impedance differential relay meets both requirements. 3 2 working principle of the c t. Also note that a. In the transient condition of saturation the c t s on both ends of the protect ed zones do not produce the correct secondary current according to the primary current.

Differential protective relay power system device function numbers a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities directional control as applied to a protective relay or relay scheme a qualifying term that indicates a means of controlling the operating force in a nondirectional relay. The differential current in the operating coil is proportional to is 1 is 2. High impedance differential relays are typically used for bus protection. Different current transformer ratios may be employed at the ends of the line.

Bus protection is an application that demands many sets of ct s be connected to the relays. In this case pickup of the protection relay is ini. The operation is independent of their magnitudes and is dependent only on their. I rest is 1 is 2 therefore the ratio of.

Phase comparison technique is the most widely used one for all practical directional distance differential and carrier relays. 0 5a 2 0 50 5 2 ii i12 tot the relay will now use 30 of this itotto derive its actual restraint current i e. It is also an application that demands the relay be able to operate with unequal ct performance since external fault magnitudes can be quite large. It is used to protect the electrical equipment against internal fault such as internal winding short circuit or bus bar phase to phase short circuit inter turn short winding puncture etc.

Differential relay working function. If the two input signals are s 1 and s 2 the output occurs when the inputs have phase relationship lying within the specified limits. The differential relay can be defined as the relay operates when the. It stats that the algebraic sum of a node in a circuit is equal to zero.

A mismatch of 1 8 is permissible. Now if idiff 0 15a relay operation. Pdf differential protection for standard power transformers has been used for decades. It works under kirchhoff s current law.

Both the input must exist for an output to occur. It is based on ampere turn balance of all windings mounted on. Principles of differential relaying the restraint characteristic suppose further that there is 0 5a sec flowing at each end. Differential relay is also called differential protection relay which is widely used in the relay protection of electric generator electromotor transformer and bus in power system.

One of the most important protection in power system is differential protection. Find read and cite all the research you. Tively matches the working point on the tripping characteristic so that it is no lon ger necessary for the user to enter charac teristic settings. Differential protection tripping can be guarded with overcurrent pickup.

Irest 0 3 x 0 5 0 15a see point p on the restraint characteristic.