ABB RELION REX640 Technical Manual page 1419

Protection and control

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1MRS759142 F

The DGMGAPC function is mainly used to protect the diesel generator from

the over/under fueling of the diesel engines and over/under excitation of the

generators. These faults are not easily detected by the traditional protection relay

algorithms, which can result in healthy generators behaving abnormally in an

attempt to maintain the system voltage and frequency within acceptable limits.

This can lead to a cascade fault in which all the healthy generators are disconnected,

leaving only the faulty unit running. Without the healthy generators to maintain

the frequency and voltage, the faulty generator will also be tripped, resulting in a

complete blackout of that part of the industrial network.

The DGMGAPC function identifies the existing network topology and the generators

are compared with the expected behavior corresponding to their operation mode or

with other generators with in the network.

Two algorithms are used to detect fueling and excitation faults, namely, Correlation

and Voting algorithms. The Correlation algorithm compares the generator behavior

with the set operation mode of the governor. If the local generator is deviating

significantly then it is identified as faulty. The Voting algorithm works on the

assumption that, generators share the load similarly. Hence a generator is identified

as faulty, if the local generation is moving significantly away from the rest of the

generators in the network. Any generator identified as faulty will not be used in

either of the algorithms.

Real and reactive power for the local generator is obtained from power

measurement function PEMMXU and for the network generator over GOOSE. As

an example, a part of application configuration with two generators is shown in

is obtained from PEMMXU and Generator2 is the network generator whose real and

reactive power are obtained over GOOSE.

Technical Manual

. Here, Generator1 is the local generator whose real and reactive power

Condition monitoring functions