Systems & Electronics

UP – UNITÀ PERIFERICA PER IL TELECONTROLLO E IL MONITORAGGIO DELLE CABINE SECONDARIE

FAULT DETECTORS AND MEASUREMENTS (RGDM) FOR SECONDARY NETWORKS

The RGDM is a device designed to be installed in the medium voltage compartment, with an SF6 or air-isolated switch, air isolated line and earth disconnecting switch, situated in remote controlled secondary substations, for protection, measurement, remote control and monitoring.

Particularly the RGDM purposes are:
• a. detecting any multi-phase and single-phase faults to earth, regardless of the MV neutral status
• b. line voltage detection;
• c. measuring the currents, voltages, active and reactive power on the MV line;
• d. dealing with faults when required, or using a remote control from UP, and opening and closing the MV RMU (according to GSCM004);
• e. interfacing with generators in the MV network, in order to coordinate voltage regulation along the line, and the remote disconnection signals (according to GSTP012);
• The device is connected to three integrated phase current/voltage sensors, CT-VT, from which the residual quantities V0-I0, V2-I2 and V1-I1 can also be obtained.
• In order to guarantee full compatibility with the RTU already in the secondary plants, the RGDM is always equipped with a double interface, able to dialogue with both the previous generation UPs and with future communications equipment.
• The RGDM is able to implement functionalities compliant to the requirements defined in IEC 62689; therefore, it is considered as a Distribution Substation Unit (DSU).
• The device has an evolved Ethernet type communication interface, by means of which it is able to exchange information in accordance with the suite of protocols provided by the IEC 61850 standard.
• The communication profile is defined in GSTP013 and is compliant with IEC61850 1st Edition and 2nd edition.

Protection functions:
Four, independent time or inverse time settable as NIT, VIT, EITLIT, SIT directional phase overcurrent 67.S1/S2/S3/S4 thresholds.
Four, independent time or inverse time settable as NIT, VIT, EIT LIT, SIT phase overcurrent 51.S1/S2/S3/S4 thresholds. These thresholds is selectable exclusively with 67 thresholds.
Three, independent time or inverse time settable as NIT, VIT, EIT LIT, SIT directional earth overcurrent 67N.S1/S2/S3 thresholds.
Three, independent time or inverse time settable as NIT, VIT, EIT, or LIT, earth overcurrent thresholds 51N.S1/S2/S3.
Maximum active power directional threshold 32P.
Second harmonic return, for inrush currents 2ndH REST.
Two threshold of 59N
One threshold of 59V2
Directional intermittent earth arc detection 67N.S4
Discrimination between voltage present/absent (27)
All the protection functions, excluding 32P and 47, have the “Breaker Failure” control, for monitoring the circuit breaker opening / closing times.
All the maximum current thresholds (51/51N and 67/67N) have the “Cold Load Pickup” function, by means of a TCLP timer that allows delaying the intervention from non-energized lines.

Automation function:
Quick re-closing cycle for the switch; selectable for all thresholds protection.
Logic selectivity of the faulty section.
Sending / receiving signals and commands, via evolved IP type networks, in accordance with the IEC 61850 standard.
Quality and measurement monitoring functions:
Measurement of electrical V, I, P, Q and cosφ quantities.
Monitoring of currents and voltages (harmonics in the node).

DG management functions:
Regulation of the voltage profile along the line, by means of static converter control.
PI control and remote disconnection of DG.
Prevention of PG tripping for DG logic selectivity.

RGDAT is a device designed to be installed in the MV bays of remote controlled secondary substations in order to detect the presence of faults and power failures on the line. The MV line is monitored by means of 3 current transducers (CT), supplied with the device, and using the voltage signals delivered by the capacitive dividers of the switchgear.
The purpose of RGDAT is to signal the status of the section of MV line monitored via relay outputs and to provide, via a 4/20 mA analog output, an indication of the current value on one of the phases. RGDAT can be completely configured and programmed from a portable Personal Computer connected by means of the RS232 serial port. The RGDAT application program can also be updated from the PC. RGDAT is based on a powerful 32 bit microprocessor belonging to the latest generation (ARM), capable of executing 60 million instructions per second; this allows a Fourier analysis to be performed on all analog inputs, acquired at a frequency of 3000 samples per second. RGDAT includes 3 alarm relays and 8 LED status indicators, visible on the outside of the enclosure.
The device complies with the technical specification e-distribuzione GSTP001 rev. 3 and to the cybersecurity guidelines (optional).

The characteristics of the reference networks are:
• Rated voltage: from 6kV to 24kV (36kV)±10%
• Maximum current of three-phase short circuit: 16kA
• Maximum value of time constant τ of the phase unidirectional component decay: 20ms
• Maximum single phase ground fault current (insulated neutral earth): 500A
• Peak value of the unidirectional component of the current added to single-phase ground fault current (neutral compensated ): 707A
• Maximum value of time constant τ of the residual unidirectional component decay: 150ms
• Presence of homopolar Voltage in healthy network condition: 0-3V
• Harmonic content in current: within prescribed limits by EN50160
• Network rated frequency 50Hz or 60Hz