Question

What is the (global) derating factor? Write at least five derating factors.

(Book: Renewable and Efficient Electric Power Systems, Gilbert M. Masters)

Answer 1

De-rating factor means any particular factor that lowers the efficiency of the designed equipment. We can analyse the de-rating factor from electrical power system point of view as follows:

1. Any power system equipment is being designed to work in certain conditions. If one of those factor is not satisfied properly then the designed equipment will not work with it's proper efficiency. That means the equipment is being de-rated by the factor.

2. Some of the global de-rating factor which de-rates the equipment efficiency are as follows :

A. Temperature : Ambient temperature affect the device performance to a great extent.

B. Pressure

C. Burial depth of underground cable.

D. Height of the overhead conductor.

E. Thermal resistivity

F. Other surrounding factors

3. To calculate or indicate upto what extent the equipment or the device can be used or stressed, a de-rating factor is defined by the manufacturer of the power system equipment.

4. Actual design rating of the equipment is being multiplied by this de-rating factor to get the workable limits of the equipment in the defined conditions.

So this is the way we can define the global meaning of the de-rating factor and certain de-rating factor are also mentioned above.