GE LPS-O Instruction Manual page 19

1 PRODUCT DESCRIPTION
Table 1–2: LPS-O MEASUREMENT FUNCTIONS
Zone or Type
Zone 1
Zone 2 (Pilot Zone)
Zone 3
Zone 4
Out of Step Blocking (OSB)
Overcurrent Backup
Overcurrent Supervision
Fault Detector
Line-Pickup Overcurrent
Remote-Open Detectors
Line-Overload Detectors
Over/Undervoltage
Out of Step Tripping (OST)
When phase distance functions are used for a zone of protection, three individual measuring functions are
available. The algorithm that implements the variable-mho measuring functions is derived from designs that
have evolved through several different families of static analog and digital relay systems which have accumu-
lated decades of dependable and secure in-service experience.
An instantaneous overcurrent tripping function (50G) provides direct tripping for severe phase-to-ground faults.
A time-overcurrent tripping function (51G) provides time-delayed backup tripping for phase-to-ground faults.
Either or both of these ground-overcurrent functions can be controlled by the NT negative-sequence directional
trip unit, at the customer's discretion.
GE Power Management
Functions
• 3 Variable-Mho phase-distance functions with time delay
• 3 Variable-Mho phase distance functions with time delay
and
Ground directional-overcurrent functions consisting of:
IPT: Ground Trip overcurrent
NT: Negative Sequence Directional Trip
IPB: Ground Block overcurrent
NB: Negative Sequence directional block
• 3 Variable-Mho phase-distance functions with time delay
• 3 Variable-Mho phase-distance functions (reverse looking) with time
delay.
3 Variable-Mho phase-distance functions
50 — Phase-overcurrent direct trip (directional or nondirectional
50G — Ground-overcurrent direct trip (directional or nondirectional)
51G — Ground time-overcurrent direct trip (directional or nondirectional)
IT — Trip-supervision overcurrent
IB — Block-supervision overcurrent
FD
I1
ROD
Level 1 Overcurrent
Level 2 Overcurrent
Three adjustable over or under voltage detectors with time delay
3 Variable-Mho positive sequence-distance functions
LPS-O Line Protection System
1.2 INTRODUCTION
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