GE350 Feeder Protection System

also available)

• Multiple protection groups with the added flexibility of switching through a wide 

selection of overcurrent protection and control features.

• Fast setup (Quick Setup) menu for power-system setup and a simple overcurrent 

protection configuration.

• Large four-line LCD display, LEDs, and an easy-to-navigate keypad.

• Multiple communication protocols for simultaneous access when integrated into 

monitoring and control systems.

Description of the 350 Feeder Protection System

CPU

Relay functions are controlled by two processors: a Freescale MPC5554 32-bit 

microprocessor measures all analog signals and digital inputs and controls all output 

relays; a Freescale MPC520B 32-bit microprocessor controls all the Ethernet 

communication protocols.

Analog Input and Waveform Capture

Magnetic transformers are used to scale-down the incoming analog signals from the 

source instrument transformers. The analog signals are then passed through a 960 Hz low 

pass anti-aliasing filter. All signals are then simultaneously captured by sample and hold 

buffers to ensure there are no phase shifts. The signals are converted to digital values by a 

12-bit A/D converter before finally being passed on to the CPU for analysis.

Both current and voltage are sampled thirty-two times per power frequency cycle. These 

‘raw’ samples are scaled in software, then placed into the waveform capture buffer, thus 

emulating a fault recorder. The waveforms can be retrieved from the relay via the EnerVista 

3 Series Setup software for display and diagnostics.

Frequency

Frequency measurement is accomplished by measuring the time between zero crossings 

of the Bus VT phase A voltage. The signals are passed through a low pass filter to prevent 

false zero crossings. Sampling is synchronized to the Va-x voltage zero crossing which 

results in better co-ordination for multiple 350 relays on the same bus.

Phasors, Transients, and Harmonics

Current waveforms are processed four times every cycle with a DC Offset Filter and a 

Discrete Fourier Transform (DFT). The resulting phasors have fault current transients and 

all harmonics removed. This results in an overcurrent relay that is extremely secure and 

reliable; one that will not overreach.

Processing of AC Current Inputs

The DC Offset Filter is an infinite impulse response (IIR) digital filter, which removes the DC 

component from the asymmetrical current present at the moment a fault occurs. This is 

done for all current signals used for overcurrent protection; voltage signals bypass the DC 

Offset Filter. This filter ensures no overreach of the overcurrent protection.

The Discrete Fourier Transform (DFT) uses exactly one sample cycle to calculate a phasor 

quantity which represents the signal at the fundamental frequency; all harmonic 

components are removed. All subsequent calculations (e.g. RMS, power, etc.) are based 

upon the current and voltage phasors, such that the resulting values have no harmonic 

components.

Protection Elements

Protection elements are processed up to four times every cycle to determine if a pickup 

has occurred or a timer has expired. The protection elements use RMS current/voltage, 

based on the magnitude of the phasor. Hence, protection is impervious to both harmonics 

and DC transients.

NOTE

NOTE: Arc Flash protection elements are processed up to 8 times every cycle.

Product identification

The product identification label is located on the side panel of the 350 . This label indicates 

the product model, serial number, and date of manufacture.

Figure 2-3: 350 Product labels

The pink color text (i.e. Model, Serial Number, Instruction Manual, MFG. Date) is for 

reference only. The text can vary.

Mounting

Standard panel mount The standard panel mount and cutout dimensions are illustrated below.

CAUTION: To avoid the potential for personal injury due to fire hazards, ensure the unit is 

mounted in a safe location and/or within an appropriate enclosure.

1. Mount the collar of required depth (1.375” or 3”) to the unit (captive or non-drawout) 

using 4 screws (see above).

2. Mount the combination of unit and collar to the panel using 4 screws as shown above.

Figure 2-7: Mounting tabs (optional)

1. From the front of the panel, slide the empty case into the cutout until the bottom tab 

clicks into place (see above).

2. From the rear of the panel screw the case into the panel at the 8 screw positions 

shown above.

3. If added security is required, bend the retaining "V"tabs outward, to about 90°. These 

tabs are located on the sides of the case and appear as shown above.

The relay can now be inserted and can be panel wired.

P20 Cover (optional)

The IP20 cover minimizes potential dangers to users by preventing finger contact with 

electrical connections at the back of the 3 Series drawout units.

Attaching the cover

The steps for attaching the IP20 cover (optional) to the drawout unit are as follows:

Figure 2-13: IP20 Cover mounting - Drawout unit only

1. Place 4 custom standoffs (item#1) using the suggested tightening torque of 8lb-in in