GE 345 transformer protection

GE 345 transformer protection

DESCRIPTION

Protection 345 is a microprocessor-based system offering main and back-up protection protection for small and medium-sized distribution transformers. The relay features advanced algorithms, allowing automatic amplitude correction and phase amplitude correction and phase offset compensation on over twenty models of two-winding of two-winding transformers, enhanced sensitivity to detect winding earth faults to detect winding earth faults, and a choice of overcurrent elements for high overcurrent elements for phase, earth, neutral and reverse currents.

The 345 protection provides the following key benefits:

- Pluggable and compact: saves on wiring and space. 

- Several protection groups offering flexibility in the wide choice of protection and control functions for the main and emergency protection. protection and control functions for main and back-up protection. 

- Quick Setup menu for configuring and protecting the electrical system. the electrical system. 

- Large 4-line LCD display, LED and keypad.

- Multiple communication protocols and simultaneous access for easy integration with monitoring and control systems.

CPU

The relay functions are controlled by two processors: a microprocessor Freescale MPC5554 32-bit microprocessor measures all analogue signals and digital digital inputs and controls all output relays; a Freescale MPC520B 32-bit microprocessor controls all Ethernet communication protocols.

Analogue input waveform capture

Magnetic transformers are used to reduce the incoming analogue signals from the source instrument transformers. The analogue signals are then passed through a 960 Hz low-pass alias filter. All signals are then captured simultaneously by sample and hold buffers, to ensure that there is no phase shift. The signals are converted to digital by a 12-bit analogue-to-digital converter before finally being transferred to the CPU for analysis.

Phasors, disturbances and harmonics

Current waveforms are processed twice per cycle using a DC compensation filter and a discrete Fourier transform (DFT). filter and a discrete Fourier transform (DFT). On the resulting phasors fault current disturbances and all harmonics are removed. The overcurrent relay is therefore extremely safe and reliable, and will not be overloaded.

Processing AC current inputs

The DC compensation filter is an infinite impulse response (IIR) digital filter, which removes the DC component of the asymmetrical current present when a fault occurs. This is done for each current signal used for overcurrent protection. Voltage signals bypass the DC COMPENSATION FILTER. This filter prevents the overcurrent protection from being too large.

Protection elements

The protection elements are processed four times per power system cycle. The protection elements use the RMS current, depending on the magnitude of the phasor. This makes the protection impervious to harmonics and DC disturbances.