Home » 6.6kV HV Induction motor Protection
Electrical Machines

6.6kV HV Induction motor Protection

HV 6.6kV Induction motor Protection

For HV motors rated 6.6kV and above motor over current, stalled rotor, and short circuit protections shall be provided by three 3-element relays mounted on the medium voltage switchgear

Over-current protection:

The inverse time over-current element shall be set to operate at 110 to 115% of the rated full load current, to initiate a common motor overload alarm and individual display light in the control system

Stalled rotor protection:

The low set instantaneous over-current element shall be set to trip the motor at 170 to 180% of the full load current and is wired in series with a contact on the inverse time element. The time setting of the inverse time over-current element shall be below the safe operating time at rated locked rotor current for a particular motor, but shall allow a minimum two-second margin over calculated starting time under minimum voltage condition

Short Circuit Protection:

The high set instantaneous element shall be set up to trip motor at slightly above the asymmetrical value of the motor inrush current. This can be usually be achieved by setting of 160% to 175% of the locked rotor current

Ground fault protection:

Automatic tripping on detection of ground fault current shall be provided by a sensitive instantaneous over-current relay.

Differential protection:

Motors rated 2500hp and above sensitive protection against internal phase and ground faults shall be provided by three phase, self balancing differential relay. This relay shall be mounted on the switchgear and connected to three CT’s mounted in the motor terminal box

Bearing protection:

HV motors shall be provided with dual element, standard accuracy bearing thermocouples, continuously monitored to alert the operators of high bearing temperature

Related Articles

Synchronous Motor Is Not Self Starting?

S Bharadwaj Reddy

Types of AC Motors and DC Motors

S Bharadwaj Reddy

What is a Transformer Tap Changer

S Bharadwaj Reddy

Synchronous Motor Starting Methods

S Bharadwaj Reddy

Types of Generators

S Bharadwaj Reddy

Basics of AC Induction Motors

S Bharadwaj Reddy

Leave a Comment

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

6.6kV HV Induction motor Protection

WordPress Image Lightbox

Send this to a friend