Electrical Power & Protection

Over-current detector

December 2014 Electrical Power & Protection

The IKI-Overhead from Kries is used to detect over-currents, short circuits, earth faults and broken overhead lines in overhead distribution lines. Suitable for use on overhead lines with nominal voltages up to 36 kV, it can be installed and removed directly on the energised line.

In solidly earthed networks and networks with NER/NEC systems, earth faults can be indicated; and with the RTU Ponline-Butler-Overhead, a message to a user’s cellphone can indicate the type of fault and potential location. Two versions are available: the standard model provides local indication of faults by LEDs, while the radio option also provides remote transmission via the Ponline-Butler-Overhead remote terminal unit.

IKI-Overhead with radio option is capable of remotely transmitting a fault message via the Ponline system. The system consists of up to nine IKI-Overhead units and one Ponline-Butler-Overhead within a range of 25 metres. Transmission of fault type messages is sent from the IKI-Overhead to the Ponline-Butler via a short range radio link, while transmission of messages between the Ponline-Butler and the Ponline-Master is done via a GSM-link.

In case of a line break, the IKI-overhead (radio option only) reads a line current below 3 A for at least 10 seconds and the IKI-Overhead sends a message to the Ponline-Butler-Overhead. The Butler collects the messages from all IKI-Overheads within its tuning range and decides whether the condition for asymmetric undercurrent is given (eg, only phase L1 undercurrent, phases L2 and L3 on normal load condition). In case of an asymmetric undercurrent, Ponline-Butler-Overhead will send a fault message to Ponline-Master. In case of symmetric conditions (all phases below 3 A or all phases on load condition) no message will be sent.

Reset of this fault condition is done automatically after re-establishment of at least a 3 A primary current on all phases for at least 10 seconds. Asymmetric undercurrents are only reported by the Ponline message and not optically via LEDs on the IKI-Overhead. If the IKI-Overhead is in normal operation mode, the alarm indication can be tested. The magnet adaptor has to be positioned close to the test/reset mark. Thus the IKI-Overhead is switched into alarm mode and the light begins to flash in a cycle of 0,5 s on – 0,5 s off. For 5 s the IKI-Overhead is in alarm mode and all internal measurement systems are switched off. Additionally the radio-option sends an alive-message to the Butler.

IKI-Overhead meets IP68 requirements and has an ultra-bright alarm indication that is easily visible, even in extreme sunlight. It is also applicable for closed loop networks and networks with secondary feeders, such as wind turbines or generators, when an automatic reclosing function is used at one feeder side.

For more information contact Paul Van As, Surgetek, +27 (0)11 792 1303, info@surgetek.co.za, www.surgetek.co.za

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