GE 850 User Manual

7–38 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
HARMONIC DETECTION CHAPTER 7: MONITORING
Harmonic Detection
The Harmonic detection 1(6) element monitors the selected 2
nd
to 5
th
harmonic or Total
Harmonics Distortion (THD), which is present in the phase currents. The relay provides six
identical Harmonic Detection elements.
During transformer energization or motor starts, the inrush current present in phase
currents can impact some sensitive elements, such as negative sequence overcurrent.
Therefore, the ratio of the second harmonic to the fundamental magnitude per phase is
monitored, while exceeding the settable pickup level, an operand is asserted, which can be
used to block such sensitive elements.
During startup or shutdown of generator connected transformers, or following a load
rejection, the transformer can experience an excessive ratio of volts to hertz, that is,
become overexcited. Similarly, the ratio of the fifth harmonic to the fundamental
magnitude can be monitored to detect the overexcitation condition.
NOTE
NOTE:
The harmonics monitored in this element is calculated from the phase currents, unlike the
second or fifth harmonic differential current used in the transformer differential element.
NOTE
NOTE:
The harmonics are updated every protection pass. The THD is updated every three cycles,
which is not recommended as a blocking signal.
Path: Setpoints > Monitoring > Harmonic Detection > Harmonic Detection 1(X)
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Configurable
Default: Disabled
SIGNAL INPUT
Range: dependant upon the order code
Default: CT Bank 1–J1
HARMONIC
Range: 2nd, 3rd, 4th, 5th, THD
Default: 2nd
This setting selects the specified harmonic or THD to be monitored. The harmonic or THD
is expressed in percent relative to the fundamental magnitude.
PICKUP
Range: 0.1 to 100.0% in steps of 0.1%
Default: 20.0%
PICKUP DELAY
Range: 0.000 to 60000.000 s in steps of 0.001 s
Default: 0.000 s
PHASES FOR OPERATION
Range: Any One, Any Two, All Three, Average
Default: Any One
This setting defines the phases required for operation, and the detail is explained below:
– ANY ONE: At least one phase picked up.
– ANY TWO: Two or more phases picked up.
– ANY THREE: All three phases picked up.

GE 850 Specifications

General

Brand	GE
Model	850
Category	Protection Device
Language	English

Summary

850 Feeder Protection System

Front Control Panel Interface

Common Setpoints

Provides a general description of common setpoints and their operational characteristics.

Device

Covers device configuration modes (Simplified/Regular) and custom configuration options.

Current Elements

Details various current-based protection elements like TOC, IOC, and directional overcurrent.

Trip and Close Circuit Monitoring

Local Control Mode (breakers and switches)

Details local control operations for breakers and switches via front panel or contact inputs.

FlexLogic

Explains the arrangement of internal digital logic and user-programmed parameters for flexible control.

Specifications

Provides detailed technical specifications for the device, including protection, input/output, and communication parameters.

Software Interface

Voltage Elements

Introduces undervoltage, overvoltage, and frequency protection elements.

Breaker Health

Breaker Failure (50BF)

Details the Breaker Failure scheme for detecting and responding to breaker failures.

Testing

Fault Reports

Cautions and Warnings

Outlines safety indicators, general precautions, and specific warnings for installation and operation.

Working with Setpoints & Setpoints Files

Security

Explains Basic Security and CyberSentry features, including roles, password complexity, and AAA server authentication.

Autoreclose

Covers the Autoreclose scheme for automatic reclosing after faults.

Transient Ground Fault Detection