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A general breakdown of commissioning of the Sigma 3 would involve the following:
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Review of installation and condition of unit
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Verification of connections
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Verification of settings
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Energization of Sigma 3
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Functional Verifications:
o
Test and Reset
o
Pulsing
o
Communication with the Sigma3-TDM
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Current injection (primary or secondary) to verify GND Fault functionality
- NGR short circuit test
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NGR open circuit test
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Offline Calibration (may be initially omitted if NGR > 20Ω)
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Energization of system
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Online Calibration (if system zero sequence impedance noticeably changes while online)
10.1 Calibration Procedure
1. Introduction
1.1 Calibration of the Sigma3 may or may not need to be performed.
1.2 Calibration of the Sigma3 may need to be done if it is experiencing nuisance NGR faults or if it is failing to
produce an NGR fault on the short circuit test or open circuit test.
2. Description of General Procedure
2.1 Perform Pre-calibration: Measure HF1 current and adjust if needed (see 4 below)
2.2 De-energize the system.
2.3 Perform Offline Calibration: Calibrate the sensitivity of the Sigma3 NGR fault lower threshold
Alternately:
Perform Online calibration using the Sigma3-TDM touchscreen display module. Skip to section 6 below.
3. Required Equipment
3.1 DC micro ammeter; scaled 0-1mA: 0-100%
3.2 Wire to partially short the NGR
4. Pre-Calibration Procedure
4.1 Measure the HF1 current to verify if it is between 10mA and 25mA. If it is not, adjust as follows:
4.2 Remove the cover from the Sigma3.
10. COMMISSIONING
