Siemens SG8158-00 manual Glossary

Glossary

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Forward Parameter setting of several ISGS functions that allows the directional protection element to pickup on fault current only in the direction of normal power flow.

High-Set Instantaneous Neutral or Ground Overcurrent (50HSN) A relay function that protects against a neutral or ground overcurrent condition. Tripping occurs when the neu- tral or ground current exceeds the programmed pickup at 100%. When tripping occurs, the actual condition that caused the trip is recorded in the device's nonvolatile trip log.

High-Set Instantaneous Phase Overcurrent (50HS) A relay function that protects against a phase overcurrent con- dition. Tripping occurs when any one phase current exceeds the programmed pickup at 100%. When tripping occurs, the actual condition that caused the trip is recorded in the device's nonvolatile trip log.

Impedance Parameter of several ISGS protective functions that set the angle used by this function. Impedance deter- mines the direction of current flow being measured and can be set from 0 to 90 degrees in steps of 1 degree.

Instantaneous Neutral or Ground Overcurrent (50N) A relay function that protects against a neutral or ground over- current condition. Tripping occurs when the neutral or ground current exceeds the programmed pickup at 100% or drops below the pickup at 95% for a period of time equal to the delay time setting. The pickup must remain active for the entire delay time for a trip to occur. If the overcurrent condi- tion subsides in less time than the delay time, the pickup will go inactive and the instantaneous neutral or ground overcur- rent function will reset. When tripping occurs, the actual con- dition that caused the trip is recorded in the device's nonvolatile trip log.

Instantaneous Phase Overcurrent (50) A relay function that protects against a phase overcurrent condition. Tripping occurs when any one phase current exceeds the pro- grammed pickup at 100% or drops below the pickup at 95% for a period of time equal to the delay time setting. The pickup must remain active for the entire delay time for a trip to occur. If the overcurrent condition subsides in less time than the delay time, the pickup will go inactive and the instantaneous phase overcurrent function will reset. When tripping occurs, the actual condition that caused the trip is recorded in the device's nonvolatile trip log.

Intelligent SwitchGear System (ISGS) High-speed, numerical, microprocessor-based protective relay designed to be easily incorporated into a computer monitored medium voltage power system.

ISGS see Intelligent SwitchGear System

LCD Two-line by sixteen character liquid crystal display that allows the viewing of parameters, real-time data, keypad entries, and messages.

logical input Input to a function internal to a relay, such as a blocking input for a function. Logical inputs can only be activated if matrixed to a physical input.

logical output Output of a function internal to a relay, such as logging an event.

matrixing Process of assigning inputs (actions) to outputs (reactions).

Negative Sequence Voltage (47N) Relay function that protects against a negative sequence voltage condition using a definite time or inverse time characteristic. Tripping occurs when the percent of negative phase sequence voltage exceeds the preset value for a specified time. This function resets instantaneously when the negative sequence voltage drops below pickup.

Neutral Time Overcurrent (51N) A relay function that protects against a neutral overcurrent condition by using a selected time overcurrent characteristics curve to determine the trip time. Tripping occurs when the neutral current exceeds the programmed pickup at 100% or drops below the pickup at 95% for a period of time equal to the delay time setting. The pickup must remain active for the entire delay time for a trip to occur. If the overcurrent condition subsides in less time than the delay time, the pickup will go inactive and the neutral time overcurrent function will reset. When tripping occurs, the actual condition that caused the trip is recorded in the device's nonvolatile trip log.

overcurrent fault protection Process where current sig- nals from sensors are converted to digital voltages by a resis- tor network and analog to digital converters in a trip unit. The digital voltages are stored in temporary memory. A protection microprocessor reads these voltages and compares their values to the set of values entered by the user. When the microprocessor detects an overcurrent condition, it's soft- ware begins to process a defined protection function. During the process of the protection function, the microprocessor continues monitoring the incoming current level data. If the overcurrent condition continues until the processing is com- pleted and the defined delay time has elapsed, a trip com- mand is issued by the microprocessor. The trip command causes an output signal to be sent to a coil in the tripping actuator.

Overfrequency (81O) Relay function that protects against an overfrequency condition. Tripping occurs when the fre- quency exceeds the programmed overfrequency pickup for a period of time equal to the delay time setting. The pickup must remain active for the entire delay time for a trip to occur. If the overfrequency condition subsides in less time than the delay time, the pickup will go inactive and the overfrequency function will reset. When tripping occurs, the actual condition that caused the trip is recorded in the device's nonvolatile trip log. Pickup occurs when the frequency in greater than the pickup setting.

parameter set Many protective functions of an ISGS relay offer two sets of parameters—set A and set B. Each set can be selected to be the active set that controls the relay. Sepa- rate parameter sets are useful for seasonal or special opera- tion settings.

G-ii Siemens Energy & Automation, Inc.