What is line differential protection?
Line differential protection is one of the most popular forms of transmission line protection. This type of protection is based on Kirchoff’s current law, which states that the current flowing into a line must be equal to the current flowing out of the line.
What is SEL 311L?
Use the SEL-311L Line Current Differential Relay with integral four-zone distance backup for easy-to-apply, high-speed line protection. Apply subcycle current differential protection with included four-zone distance and directional overcurrent backup.
For which of the following ratings of the transformer differential protection is recommended * 1 point?
For transformers rated at 5 MVA and above that are important to system operation, or where high sensitivity is necessary (generator transformers), differential protection is recommended in addition to high- and low-side overcurrent relays.
What is percentage differential protection?
The percentage differential relay is designed to operate the differential current in terms of its fractional relation with actual current flowing through the circuit. It is used to protect the system under Current transformer saturation, unequal CT ratios, nuisance trip etc.
How is a transformer protected?
The protection of a transformer against the overloads is performed by a dedicated protection usually called thermal overload relay. This type of protection simulates the temperature of the transformer’s windings.
Which relay is used to detect and protect internal faults of a transformer?
Buchholz relay
Buchholz relay is a gas actuated relay and it is used to protect the transformer against all internal faults.
What is the difference between differential and percentage differential relay?
Definition: The percentage differential relay is defined as the relay that operates on the phase difference of two or more similar electrical quantities. It is the advanced form of differential protection relay. The only difference between them is the restraining coil.
What happens in a differential relay when the saturation is too high?
Overexcitation conditions. Overexcitation of a transformer could cause unnecessary operation of transformer differential relays. When the primary winding of a transformer is overexcited and driven into saturation, more power appears to be flowing into the primary of the transformer than is flowing out of the secondary.
What does the sel-311l do?
This instruction manual covers the SEL-311L, a digital line current differential relay with integrated communications interfaces.
How do you use the SEL 311l line current differential relay?
Use the SEL-311L Line Current Differential Relay with integral four-zone distance backup for easy-to-apply, high-speed line protection. Apply subcycle current differential protection with included four-zone distance and directional overcurrent backup.
How to get local measurement from sel311l HMI?
Inject three phase voltage and current as nominal and take measurement from (SEL311L HMI) b. Another method: click ‘Terminal tool’ icon. c. To get local measurement Type command as ‘MET B’ at Terminal tool. It is described by the picture below.
Is the English language manual the only approved SEL manual?
The English language manual is the only approved SEL manual. Copyright © SEL 2001 (All rights reserved) Printed in USA.