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 Short Circuit Current Indicators for Cable HV lines
These devices are designed to show over-currents in a line on a short circuit connection between two or three phases and to show over-current between a phase line and the ground on high voltage cable lines.
Characteristics - Indication of overcurrents in cable high-voltage lines on a short circuit connection between two or three phases or between a phase line and the ground
- The network phase-ground short limitation by a resistor to 300 Aeff or more required
- Contactless installation
- Indication either through opening relay contacts or through signal light flashing
Applications The INKA K1, K2 Short Circuit and Ground Connection Current Indicator is designed to show overcurrents in a line on a short circuit connection between two or three phases and between a phase line and the ground on high voltage cable lines. The current between a phase line and the ground has to be limited to 300 Aeff or less by a resistor. The indication is provided with an electric contact, transmission to the control room via a radio link and optically through a flashing indicator. The instrument is to be located at a safe distance (about 30 to 80 centimeter - 12 to 32 inches) from the cable line, on the cable lead inner wall or door, symmetrically to all phases if possible. The instrument is galvanically isolated from the high voltage cable line system. The instrument is powered from an accumulator which is recharged from the low voltage (230 Veff) mains. It has plastic case for installation on a wall or the DIN 35-millimeter strip. The high voltage cable line system condition is monitored through measuring and evaluating the magnetic field level and its changes. Further the line low voltage (230 Veff) is monitored. The failure conditions (short circuit current between phase lines and limited current between a phase line and the ground through the resistor with subsequent loss of voltage) are indicated in several ways, depending on the Indicator model and its options. Indication is through a relay opening contact, using radio communication and optical indication with a flashing light. All the types of indication can be combined with each other. Further the indicator status can be transmitted via an RS-232 serial link. The failure signal level is set up automatically, depending on the cable line system operating condition. Other constants are preset in the factory, yet they can be readjusted by the user or on the spot of application using a Personal Computer. The constants can be set and the values and conditions measured can be transmitted from the Indicator via an RS-232 serial link. There is optional software for a Personal Computer to set parameters and read data. Operation Description If failure is detected, the relay gets opened and the optical indication flashes in 2.5-second periods. A failure is evaluated when concurrently detecting the following conditions on the cable: - there has been a steep current increase, exceeding a preset limit of 80 milliseconds
- the current increase has been followed by a loss of voltage for longer than a preset time.
The failure indication is cancelled when the voltage comes up again for a preset time or longer. This filters out a false indication on the mains recovery, successful automatic switch-on attempt and when working on the cable line system. Indicator models and add-on modules in production - INKA-K1 Indicator - an intelligent contactless sensor for installation at cable lead. There are designs for installation onto a wall using two screws or for installation on a DIN 35-millimetre strip. A screened multiwire cable, up to 8 metres long as agreed on with the customer, is used for connecting to the INKA-150-pwr power supply unit.
- INKA-K-pwr Module - a power supply module for recharging the accumulator, a switchboard module and a module for indicating voltage in the cable line system. The module is for installation on a DIN 35-millimetre strip. It includes a connector for a serial communication link with the RS-232 type interface. The link can be utilised to change some of the preset parameters, for monitoring the data measured and for servicing purposes.
- INKA-K-aku Module - an accumulator module for installation on a DIN 35-millimetre strip. The accumulator powers the Indicator and indication on power supply voltage failure.
- INKA-K-opt Module - a module of optical indication for installation on a wall, vertical bar or a DIN 35-millimetre strip. It is to be located outside the station so that it is visible from an accessible point.
- INKA-K-rad Module - a radio communication module for installation on a DIN 35-millimetre strip. The antenna is rod or Yagi. It is to be located outside the station, as the transmission conditions require.
- INKA-WK Program - software to run under Microsoft Windows 95/98. The program can be utilised to change some of the preset parameters, for monitoring the data measured and for servicing purposes
Technical Parameters | Measured distribution line | | | number of phase wires | 3 | | voltage range | 6 - 35 kV | | current | 0 - 300A | | Digital outputs | | | number | 2, isolated contact | | maximal load | 60 V / 200 mA | | Serial link | | | interface | RS-232 | | rate of transmission | 1200 Baud | | maximum distance | 12 m | | Radio Communication (preliminary) | | | frequency | 433,92 MHz | | rate of transmission | 1200 Baud | | maximum distance | 200 - 500 m | | Power supply | | | AC (NN power supply) | 200 to 250 V / 3 VA | | accumulators | 12 V / 2,5 Ah | | Physical parameters | | Enclosure | IP 65 | | dimensions (W + H + D) | | | - indication | 55 x 65 x 37 mm | | - with optical signalization | 125 x 75 x 90 mm | | material | polykarbonat | | operating environment | class D1 as in IEC 654-1 | | temperature | | | - operating | -25° to+70° C | | - storage | -40° to +85° C | | relative humidity | 0 to 100 % | |
