GE SFF202B1A Static Frequency Relay

The GE SFF202B1A monitors power system frequency for protection applications. This static relay detects underfrequency or overfrequency conditions quickly. You will find it in generator control panels and utility substations. It provides two independent frequency setpoints with adjustable time delays. Therefore, this unit prevents damage from abnormal grid frequency events.

This relay measures 140 mm in height and 85 mm in width. Its depth reaches 110 mm for standard panel mounting. The unit weighs approximately 0.55 kilograms. It contains four main circuit boards with solid-state components. Two frequency detection circuits operate independently from each other. Additionally, you get two output relays for tripping or alarming.

Key Technical Specifications

Parameter	Value
Manufacturer	GE Multilin / General Electric
Model	SFF202B1A
Product Type	Static Frequency Relay
Frequency Range	45 to 65 Hz
Underfrequency Setpoints	2 (adjustable)
Overfrequency Setpoints	2 (adjustable)
Time Delay Range	0.1 to 10 seconds
Measurement Accuracy	±0.02 Hz
Voltage Input	120 VAC or 240 VAC
Auxiliary Power	24-250 VDC / 48-250 VAC
Height	140 mm
Width	85 mm
Depth	110 mm
Weight	0.55 kg
Output Contacts	2 Form C (SPDT)
Output Rating	5A at 250 VAC
Number of Circuit Boards	4
Energy Storage	≈ 850 µF (capacitive)
Operating Temperature	-20°C to +70°C

Internal Architecture and Energy Storage

The GE SFF202B1A stores moderate energy in its power supply section. Electrolytic capacitors hold approximately 850 microfarads of total capacitance. These capacitors provide hold-up during brief AC interruptions. A digital signal processor measures incoming frequency eight times per cycle. This DSP compares the measured value against four user-defined setpoints. Two independent comparators generate trip signals when frequency deviates. You get separate LEDs for power, pickup, and trip indications.

Connection Interfaces and Wiring Details

You will find a 14-pin terminal block on the rear panel. This terminal accepts voltage inputs, power, and output wiring. Connect the AC voltage input to terminals 1 and 2. Apply auxiliary power to terminals 3 (positive) and 4 (negative). The GE SFF202B1A automatically accepts AC or DC control power. Wire each output relay to terminals 5-6-7 and 8-9-10. Use 14 AWG stranded wire for all power connections. Keep control wiring separate from power wiring inside the panel.

Configuration and Installation Steps

You mount this relay onto a standard DIN rail or panel. First, set the four frequency pickups using front dials. Adjust each dial to your desired underfrequency or overfrequency value. Then, set the time delay for each pickup separately. Slide this relay onto 35 mm DIN rail until it snaps. For panel mounting, use four M4 screws through the housing. Connect the voltage source and auxiliary power securely. The GE SFF202B1A draws only 5 VA from the supply. Test each setpoint with a frequency calibrator before commissioning. Verify that both output relays operate at the correct frequencies.