GE Industrial Solutions Entellisys System User Manual - Manual (Page 57)

Single Point Relay protection 57
5
5.1.3.4 Usage
The GF Protection function detects unintentional current flowing from a circuit to a conducting
path to ground. These currents are usually of a lower magnitude than the current set by the LT
pickup setting and would not normally be sensed by that protection function. GF protection is
performed by calculating the vector sum of the three phase currents in a three-wire system or
the vector sum of the three phase currents and the neutral in a four-wire, wye-system and
comparing this sum to a pickup threshold.
GF pickup, trip, and dropout events are recorded in the Entellisys Sequence of Events log.
Waveforms and fault reports are also captured on an GF trip event, and can be viewed from the
Sequence of Events log.
5.2 Single Point Relay protection
Entellisys system provides Single Point Protection Relay functions in three optional packages:
the Voltage Relays package, the Frequency and Reverse Power Relays package and the High
Current Relay package.
The Voltage Relays package includes the following functions:
• Undervoltage
• Overvoltage
• Phase Loss Protection
The Frequency and Reverse Power Relays package includes the following functions:
• Under Frequency
• Over Frequency
• Reverse Power Protection
The High Current Relay package includes the following function:
• High Current Protection
NOTE: Removing a relay package from a Messenger can cause any control scheme that
includes those relays to misoperate. See
Options on page 37 for more details.
These protection relay functions run in addition to the standard overcurrent protection
functions and are performed at the Entellisys CPU only. No protection relay functions are
performed locally at the Messengers.
Each relay has two sets of pickup and delay settings, with the exception of the High Current and
High Resistance GF. One set is for tripping the circuit breaker and the other is for activating an
alarm. Therefore, a user can set one threshold for a trip condition and the other threshold for an
alarm condition. It is possible to enable or disable each relay function individually; for example,
it is possible to enable a relay alarm function but disable the trip function.