The Current Counter Mk II has been designed to make the best use of modern techniques in electronic design to produce a versatile, robust unit capable of achieving many years of reliable service in the electrically onerous conditions often found in electricity supply sub-stations. The unit is based around a well-proven single-chip microprocessor and is built on a single multi-layer printed circuit board. This, together with the comprehensive filtering circuits included on all input lines, gives interference immunity (both ESD and radiated) which exceeds the current levels required by legislation (CE approval). In addition the unit fully meets the CE requirements regarding radiated and conducted emissions. The unit is housed in a sealed plastic enclosure which is coated on the inside, again to control radiated emissions and susceptibility. A liquid crystal display with LED backlight has been used to provide the optimum performance and versatility together with low current consumption and long life. The membrane-style control panel and key switches again provide reliable programming and data retrieval controls without compromising the sealed nature of the unit. The software has been written to provide an intuitive operation avoiding the need for detailed perusal of an instruction manual. The set-up and data viewing modes are all menu driven and the information on the display gives the operator details of options at each stage. Indeed it should be possible to set up and use the unit without referring to written instructions at all. Full use has been made of the versatility of a microprocessor-based unit to provide many features (both standard and optional) which were not available on the previous Current Counter models.

• CONDITION MONITORS OIL, SF6 and VACUUM BREAKERS
• Maximum Phase Current per trip
• Cumulative MVA Interrupted
• Historical record of last 5 trips
• Actual Tripping Time
• Local & SCADA interface
• 80% Pre-set Current
• 100% Lockout
• Slow Tripping Times

• REDUCES UNNECESSARY MAINTENANCE
• REDUCES MAINTENANCE COSTS
• INCREASES CIRCUIT BREAKER UTILISATION

The Current Counter MKIII is easier to install than previous models and also measures and displays maximum values of fault current in each phase, various cumulative current values, useful percentage values breaker tripping times.

Oil CB
Assume it is engineering policy to complete post fault maintenance after 6 fault trips. At 11 kV with a system fault level of 25OMVA the maximum cumulative fault duty would be 1500MVA. However, if all faults were 5OMVA each and with Current Counter installed, there would be 30 fault operations recorded before the circuit breaker had interrupted the equivalent of 1500MVA.

BENEFIT — Current Counter would reduce the cost of manpower, transport and materials because post fault maintenance would have been saved on 5 separate occasions.

SF6 and VCB
Manufacturers of SF6 and vacuum breakers have published limits for cumulative fault current interrupted/number of operations. These values must not be exceeded and Current Counter provides the means to monitor and control fault duty.

BENEFIT — Current Counter not only provides an historical record of fault current interrupted, but establishes a base for determining future maintenance policies on this type of switchgear.