MainsPro G99TT 1.0.0 Global Guide
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Note: ROCOF is sensitive to voltage jumps, therefore it is recommended to be disabled during tests of
overvoltage and enabled after tests are finished.
8.7 Phase rotation, incorrect phase polarity
MainsPro G99TT provides check of the phase sequence and polarity. The correct connection is indicated in
the wiring instructions e.g. on MainsPro G99TT box or in chapter Wiring (page 11), where clockwise rotation
system is expected on the mains side. It may happen, that e.g. by redesign in the mains or generator site
installation, the phase rotation changes. MainsPro G99TT ensures in such case, that this state is indicated
and it prevents incorrect closing of the circuit breaker by its standard protective functionality. To allow phase
sequence or incorrect phase polarity check, the phase angle between the 3 voltage vectors is expected in
range 120° +/- 30°. If a wrong phase arrangement is detected, TRIP (page 31) is issued and the appropriate
LED signalization is given. The reconnection of measurement terminals is necessary to ensure further proper
functionality of the unit.
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