Line Current Differential Protection (ANSI 87L): Functions, Protection Zone and Applications
The ANSI/IEEE device function number for line current differential protection is 87L. Its operating principle is based on comparing the currents measured at all line terminals and determining whether a fault is internal by calculating the difference between the currents entering and leaving the protected zone. Hereinafter, it is referred to as “line current differential […]
2026-08-31
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Line Current Differential Protection (ANSI 87L): Operating Principle and Restraint Characteristic
Line current differential protection (ANSI 87L) is a communications-assisted unit protection scheme that compares the currents measured at all terminals of the protected line. It is normally applied as the main protection for the line. The protection operates according to Kirchhoff’s current law. Current transformers (CTs) are installed at both ends, or at all terminals, […]
2026-08-31
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Motor Thermal Overload Protection (ANSI 49): Operating Principle and Setting Calculations
1. What Is ANSI 49 Protection? ANSI 49 is a protection function designed to prevent motor damage caused by excessive temperature and accumulated thermal stress. It is commonly referred to as: Motor Thermal Overload Protection Motor Thermal Model Protection Motor Thermal Replica Protection The function uses motor current, operating time, current unbalance, cooling conditions, and […]
2026-08-29
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Generator Negative-Sequence Overcurrent Protection (ANSI 46): Principles, Functions and Setting Calculations
1. Protection Configuration Overview Generator negative-sequence overcurrent protection (ANSI 46) detects stator negative-sequence current arising from power-system unbalance and protects the rotor against the resulting thermal damage. It responds primarily to phase-to-phase faults, phase-to-phase-to-ground faults, open-conductor conditions, incomplete-pole operation of circuit breakers, and prolonged severe load unbalance. A single-phase-to-ground fault may also produce negative-sequence current, […]
2026-08-29
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Generator Protection System Selection Guide
1. General Overview GoWatron provides generator protection solutions for low-voltage generators, small and medium-sized generating units, unit-connected generator-transformer applications, and complete generator protection and control systems. The appropriate solution should be selected according to: Rated generator voltage and output Generator and step-up transformer connection arrangement Required protection functions Requirement for rotor earth-fault protection Integrated or […]
2026-08-29
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DNP3.0 (IEEE 1815) vs IEC 60870‑5‑104 Key Differences
DNP3.0 is the mainstream SCADA protocol for North‑American power systems. IEC 60870‑5‑104 is an IEC international standard and the predominant telecontrol protocol in China and Europe. Both protocols implement four‑remote functions (remote indication, remote measurement, remote control, remote adjustment) and support TCP/IP Ethernet communication. However, they differ significantly in protocol architecture, data model, message frame […]
2026-08-22
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Neutral Point Voltage Differential Protection（ANSI 87V） for Double-Star Capacitor Banks: Principle and Setting Calculation
Protection Overview Neutral point voltage differential protection for double‑star capacitor banks, commonly referred to as double‑star neutral unbalanced voltage protection in field engineering, is a dedicated primary protection designed for internal fault detection of ungrounded high‑voltage shunt double‑star capacitor assemblies. A dedicated voltage transformer (VT) is installed between the neutral points of two electrically independent […]
2026-08-22
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Configuration of Generator Protections and Their Respective Functions
GoWatron provides a full range of synchronous generator protection solutions. This page outlines the standard configuration of generator protection systems and the corresponding functions of each ANSI device number, covering differential protection, stator ground fault protection, loss-of-field protection, reverse power protection, negative-sequence protection, and other widely applied generator protection functions. Manufactured by GoWatron, the GWPR300-GRE […]
2026-08-18
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