CT Lab, which is located in Stellenbosch, was established in 1994, and specialises in providing total solutions in the electrical power quality and insulator pollution monitoring fields.
The company develops and manufactures its own electronic measurement and recording devices for these applications. With an instrument base approaching 1500 units, CT Lab has grown to become the largest supplier of power quality recorders in the country. The company will sell its instrumentation but also offers a service where it sells data to customers and remains responsible for taking care of the instrumentation and technical issues. While development is in-house, part of the manufacturing is sub-contracted out with CT Lab doing the final assembly, testing and calibration.
CT Lab has developed an on-line leakage current analyser (OLCA) which is capable of monitoring leakage current present on high voltage insulators or bushings while they are in service. The same instrument also records the different weather parameters simultaneous with the leakage current data. These weather parameters include temperature and humidity, wind speed and direction, rainfall and UVB irradiation. The OLCA is a microprocessor-based data acquisition system and can record leakage current activity on nine different components. It operates in a standalone mode and all captured data is stored on board for later retrieval via an RS232 port or through an external dial-up modem. The OLCA can be powered from mains or 12 V d.c. and with a total power consumption of under 30 W, solar power could be used.
Leakage current data is useful for a number of reasons, some of these being:
* Rating of insulator profiles and materials exposed to the same environment.
* Study of the effects of leakage current on material ageing.
* Determination of the mechanisms of flash-over.
* Direct indication of pollution levels.
* Determination of the environmental parameters that have the largest effect on ageing.
While Eskom is the largest local customer of CT Lab, with a 1400-channel system at Koeberg alone, the company has installations in Dungeness (England), STRI (Sweden), IEC (Israel) and STEG (Tunisia), EPRI Lennox (USA) and PPC (Greece).
Power quality is an issue that has become of major importance to both electricity suppliers and consumers with a need for the supply to be continuously-monitored while consumers need to monitor their own contribution to power quality. There is also a need to establish a relationship between equipment failure and power quality and to ensure proper specification of equipment connected to the grid.
CT Lab has been active in the power quality (PQ) field since its inception and during 2001 launched its new generation PQ monitoring equipment for both the local and international markets. The new products are based on the latest international PQ specifications and requirements and also include many practical enhancements required by users. CT Lab offers not just the instrumentation but also software for fully remote operation, databases for the captured data and software that enables interpretation of the data and to generate reports and graphical outputs. As CT Lab believes that the day of the standard product is at an end, so its software is fully customisable and can be used in conjunction with the Internet.
The flagship product from CT Lab is its ImpedoGraph which is a three-phase power quality monitoring instrument that complies with all the latest standards. The output from the instrument includes detailed diagnostic data for each PQ event including wave shapes with pre and post data and all relevant phase information. The phase and diagnostic information is then used to calculate dip, flicker and harmonic emissions. The fully automated data management software has a graphical data viewer and report generator. As the ImpedoGraph is Internet-enabled all data can be accessed remotely via the Web. The data is also available through an RS485/RS232 telemetry interface. Time is managed through a GPS time synchronisation port and can be synchronised relative to other instrumentation or absolutely, using a GPS time source. The instrument uses high voltage capacitors to enable it to 'ride through' dips less than 10 seconds. If a longer time is required, an external UPS can be installed. The latest ImpedoGraph features additional communications interface options, these including Ethernet (UTP) and a scada interface. The Ethernet connection allows the equipment to be connected onto existing networks. The scada interface allows for example a PLC to request the instantaneous power factor value from the instrument and it can then switch in capacitor banks to control the power factor to an acceptable level. The PQ parameters recorded by the ImpedoGraph include voltage and current.
The VectoGraph, which is widely used in South Africa, is a three-phase voltage quality recorder that is capable of monitoring all relevant voltage quality parameters. These include dips and surges, transient over-voltage, harmonics, RMS voltage profiles and voltage unbalance. Similar to the ImpedoGraph, it provides a fully-automated PQ data management system. The VectoGraph is field-upgradeable and new embedded code can be downloaded if required. High voltage capacitors are again provided to cope with short voltage dips.
Another instrument it supplies is its ProvoGraph voltage dip and profile recorder, a smaller version of the VectoGraph. This uses an internal lithium battery to power the non-volatile RAM and realtime clock in the absence of mains power. A separate rechargeable battery is used to support the instrument for up to 5 seconds during voltage dips or short outages.
The final product in the company's current range of PQ instruments is the MiniGraph, which is housed in a small aluminium enclosure and captures voltage regulation and voltage outages data. The MiniGraph is compliant with CT Lab's standard automated data receiving software. The instrument interfaces directly onto 230 V networks and it features low layout costs and low cost of ownership.
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