GE F60 Instruction Manual

Also see for F60: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

CHAPTER 5: SETTINGS MONITORING ELEMENTSF60 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 5-2835Some faults in overhead distribution feeders are characterized by low fault current due to high ground resistance. If thefault current is in the order of expected unbalance load or less, it cannot be reliably detected by overcurrent protection.These faults are classified as high-impedance (Hi-Z) faults. Since a Hi-Z fault is not accompanied by excessive current, it isgenerally not dangerous to the electrical installation except for some damage to the overhead conductor at the faultlocation. However, an undetected Hi-Z fault is a risk to people and property as well as having a potential to evolve into afull-blown fault.The following event types are associated with Hi-Z faults. It is assumed that for all cases that ground is involved.• High impedance fault — A fault with fault impedance sufficiently high such that it is not detected by overcurrentprotection• High impedance, downed conductor fault — A high impedance fault for which the primary conductor is no longerintact on pole top insulators, but instead is in contact with earth or a grounded object• Arcing fault — Any high impedance fault which exhibits arcingCombinations of these events are possible: for example, an arcing high impedance, downed conductor fault. The Hi-Zelement is intended to detect high impedance faults that arc and to differentiate those that are downed conductors fromthose that are not. It should be noted that no known technology can detect all Hi-Z faults.The Hi-Z element was primarily designed for solidly grounded systems. The similar Hi-Z element in the DFM200 relay hasbeen tested with some success on impedance grounded systems as well. However, there are no guarantees of certainoperation of the high impedance fault detection element on non-solidly grounded systems.The Hi-Z data collection consists of RMS Data Capture and Hi-Z Data capture:• RMS Data Capture — The RMS data captures are triggered by two-cycle Hi-Z overcurrent conditions, loss of loadconditions, and high arc confidence conditions. Captures triggered by loss of load and high arc confidence conditionsare saved to a temporary capture table, and deleted if the event does not result in an Arcing or Downed Conductorcondition. The relay maintains a history of four captures and utilizes a combination of age, priority and access fordetermining which capture to save.The RMS data capture contains the two-cycle RMS values for the voltage and current for each of the phases andcurrent for the neutral channel. The capture frequency is half the system frequency. Each capture contains 1800points.• High-Z Data Capture — Hi-Z Data Captures are triggered and maintained in an identical manner as RMS DataCaptures. The relay maintains four captures of 300 records each. The capture frequency is 1 Hz and the data collectedis defined in the following two tables.Table 5-41: Hi-Z specific data HI-Z VOLTAGE SUPVDELAY: 60 cyclesRange: 0 to 300 cycles in steps of 2 HI-Z EVEN HARMONICRESTRAINT: 20%Range: 0 to 100% in steps of 1 HI-Z TARGET:Self-resetRange: Self-reset, Latched, Disabled HI-Z EVENTS:DisabledRange: Disabled, Enabled# Name Description0 EadCounts Total number of EAD counts for the phase1 ArcConfidence ArcConfidence for the phase2 AccumArcConf Accumulated ArcConfidence for the phase3 RmsCurrent The 2-cycle RMS current for the phase4 HighROC Flag indicating a high rate of change was detected5 IOC Flag indicating an instantaneous 2-cycle overcurrent was detected6 LossOfLoad Flag indicating a loss of load was detected7 EadZeroed Flag indicating that this phase’s EAD table was cleared8 HighZArmed Flag indicating that this phase is armed for a high-Z detection