ECIT for medium voltage switchgear

Connecting the ECIT to the process bus via switches

Intelligent electronic devices (ECIT, protection relay, power meters, etc) are connected to separated process and station buses. To increase the reliability of data transmission, the LAN is backed up in accordance with IEC 62439-3 (PRP).

SV-stream merging mode is available in ECIT to optimize the process bus traffic and reduce the number of network switch ports. In this mode, ECIT merge three single-phase SV streams into a single three-phase SV stream according to IEC 61869-9.

Direct connection of ECIT to IEDs

The network architecture of the cell can be simplified if SV streams do not need to be output outside the cell. There are two options available:

• each IED is connected by patch cords with three phase ECITs;
• the three phase ECITs are interconnected by patch cords and IEDs are connected to two of them. The ports of one ECIT are configured to work with two networks, the ports of the other two ECITs are switched between each other.

In the second scheme, one of the three ECITs merge the phase SV-streams and publishes two three-phase streams in two directions: SV96 – towards the protection IED, SV288 – towards the IED of measurement and metering.

Both schemes support ECIT clock synchronization: precise phase synchronization between each other (± 1 microsecond) is performed using the IRIG-A protocol – one ECIT synchronizes the other two, general time synchronization (±1 ms) is performed from the IED using the SNTP protocol.

All-in-one for MV Protection, Automation and Metering

An additional capability of ECIT is the integration of protection, automation, metering, and measurement functions, which enables optimized implementation of protection and control schemes for medium-voltage switchgear.

Each feeder is equipped with three ECITs, one per phase. Each device measures the parameters of its phase (I, U, P, Q), records disturbance events, and synchronizes and exchanges data with the designated Master ECIT. The Master ECIT receives data from the other two phases and GOOSE messages from external IEDs then provides three-phase metering and feeder protection functions, including:

• Phase Voltage-Controlled Time-Directional Overcurrent Protection, with the possibility of acceleration via an external signal (GOOSE), 2 units – ANSI 51/51V/67 (PVOC/PDOC);
• Phase Instantaneous Overcurrent Protection with inrush current blocking function, 2 units, ANSI 50 (PIOC);
• Arc Flash Detection (based on a GOOSE signal from an external arc fault registration system – ENMV-1 + AFS), (SARC);
• Directional Earth Fault Protection, ANSI 51N/67N (PTEF/PDEF);
• Undervoltage Protection, ANSI 27 (PTUV);
• Overvoltage Protection, ANSI 59 (PTOV);
• Current Unbalance Protection, ANSI 46 (PPBR);
• Protection Busbar Blocking Logic;
• Breaker Failure Protection, ANSI 50F (RBRF).

Optionally, an HMI device can be connected directly to the ECIT for monitoring, diagnostics, and local control. It displays measurements, switchgear status, and protection data, while enabling direct control over the switchgear components. The substation automation system receives data from the ECIT using standard communication protocols. Time synchronization within the facility is provided locally by the ENCS-2 or via communication links to the network control center.

For traffic optimization in the process bus while saving the efficiency of the protection, ECIT supports the optional publication of SP streams (SP – Synchrophasors). For the proper processing of the SP-stream by the IED, support for protection algorithms based on synchrophasors is required.