PCD231B PCD231B101 ABB Excitation system control module

PCD231B PCD231B101 ABB Excitation system control module

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At IDMT characteristic, the operate time of the stage is dependent on the voltage

value: the greater the deviation from the setting value, the shorter the operate time.

Three time/voltage curve groups are available: A, B and C.

An overvoltage stage starts when the measured voltage exceeds the setting value of

the stage. An undervoltage stage starts when the measured voltage drops below the

setting value of the stage. However, the IDMT calculation does not start until the

deviation between the measured voltage and the setting value exceeds 3 percent.

The operate time accuracy stated in technical data applies when the deviation is 10

percent or higher.

Characteristics of the overvoltage stages

The IDMT characteristic curve groups A and B are designed for overvoltage stages

U> and U>>/U2>. Stages U> and U>>/U2> can be configured to use different

characteristics. The relationship between time and voltage at IDMT characteristic

can be expressed as follows:

t[s]= k 480

32 U U>

U>

0.5

+ 0.05

p

×

× ⎛

⎝

⎜ ⎞

⎠

⎟ − − (3)

t = operate time

k = time multiplier k> or k>>

U = measured voltage

U> = set start value U> or U>>/U2>

p = constant (see Table 5.1.4.6.-2)