�������� Provide innovative and reliable testing solutions to the electrical industry. Build strong bonds with our customers and listen to their needs so that using continuous improvement methods we can achieve total satisfaction.
������� in Melbourne , in 1976 by Richard Dowling (CEO) to supply the local Victoria state utility with instruments. ���� to deliver to the whole Australian market. �������� to satisfy global markets. (80% of the production is now sold overseas)
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����������������� CEO Technical Operations Financial/Admin. Sales Mngr. Mngr . Mngr. Mngr. Warehouse Service & Quality Production Internatio Accountab Accounts R&D Purchases Local Sales Personnel Calibrations Control Personnel nal Sales ility Payables & Administration ��� ����� is a medium sized company with 20 employees. This size and structure give us the advantage of a great flexibility not found on any other competitor in the market. We are able to easily double our actual production capacity without mayor investments of capital or time.
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����������������������������� CT testing : PT (VT) testing 590G CT Tester 590D-1 PT Full Load Tester 590F Live CT Tester 661 Protection CT Tester 661 Protection CT Tester CVT testing 505B Admittance Tester 590K CVT Tester 594 CT Batch Tester 820 CT Test Bridge Burden testing Reference CTs 704 CT Burden Tester
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�������������� � Primary winding The winding through which flows the current to be transformed. � Secondary winding The winding which supplies the current circuits of measuring instruments, meters, relays, etc. � Rated primary current The value of the primary current on which the performance of the transformer is based. � Rated transformation ratio � Rated transformation ratio The ratio of the rated primary current to the rated secondary current. � Current error (ratio error) （ （ （ （ CT ） ） ） ） The error which a transformer introduces into the measurement of a current and which arises from the fact that the real transformation ratio is not equal to the rated transformation ratio. � Phase displacement (CT&PT) � The difference in phase between the primary and secondary current vectors. � Burden / Secondary circuit The external circuit supplied by the secondary winding of a transformer. � Burden The impedance of the secondary circuit in VA and power-factor. � Rated burden The value of the burden in VA on which the accuracy requirements of this specification are based. � Polarity The way a CT has to be marked or connected so that the secondary current is in phase with the secondary. (Primary current INTO “polarity”; Secondary current OUT OF “polarity”)
����������������� � Usually only the meter is tested. � Meter measures only what reaches its terminals
���������������� � Even if the meter has zero error, and it is perfect, the billing may not be correct. � Sources of billing errors include: � CTs: � Incorrect accuracy class � Incorrect accuracy class � Over-burdened � Faulty � Wrong Polarity � Shorted � PTs: � Incorrect accuracy class � Over-burdened � Faulty � Wrong Polarity Shorted CT Open CT � Faulty or incorrect wiring. Produces wrong readings, NOT no readings � Loose connections.
�������������������������������������������� ����������������������������������� Theft of Administrative � Causes of metering errors. Service Error 6% 14% PT problem PT problem 8% Wiring Error Faulty Meter 38% 12% CT Problem 22%
������������������������������������� � Basic Theory � CTs should maintain current ratio from zero to full rated current. � CT ALWAYS has some errors. Real output is less than the turns ratio. � Error is due to magnetizing current in the core. � (Output current) = (Current due to turns ratio) – (Magnetizing current). � Magnetizing Current depends: � Magnetizing Current depends: � Voltage of the output (secondary) terminals of the CT � Admittance of the core. CT Equivalent Circuit. Non compensated CT error characteristic curve. (due to magnetizing current)
� CT Compensation � In order to increase the output current CT manufacturers will slightly change the turns ratio. � For example: In a 200/5 CT. with 40 turns, if instead of using 40 turns, to compensate the magnetization loss error, using 39 turns, will mean 200/5.13A (2.5% more current), this is a very big error, so CT manufacturer could connect 2 windings in paralell of different cable gauges, to minimize the extra error and try to compensate for the different cable gauges, to minimize the extra error and try to compensate for the magnetizing current. Compensated CT error characteristic curve. (error due to magnetizing current + ratio compensation)
� CT DESIGN FOR MINIMUM MAGNETISING CURRENT ERROR Magnetizing current = Voltage / Core impedance � The Output of a CT always has a large in phase component and a small leading component (caused by the lagging component subtracted from what the output current should be.) � To minimize the error, the core admittance can be made smaller: � Increase the section size of the core � Increase permeability of the core material � Increase permeability of the core material � Core cost is high so CT manufacturers try to use the smallest possible core. � THE EFFECT OF CT BURDEN � Affects the voltage on the secondary terminals (higher burden, higher voltage) � Small amount of this voltage depends on the CT winding. � This voltage increases magnetizing current � TO ACHIEVE MINUMUM ERRORS � Use CTs with maximum number of turns on the core (Minimizes magnetizing current errors) � Parallel turn compensation increases current output (Makes the ratio error more positive)
������������������� � Primary Injection � Full primary current injected into the CT (Variac + Transformer). � CT output is connected to a Burden box � Reference CT to do Nulling test Good Points: Good Points: � Theoretically good accuracy Bad Points: � Accuracy depends on many components � Not practical for field testing � Heavy and bulky to carry � Large testing times � Expensive � Difficult to connect (needs specialized personnel) � Limited selection of Power Factors � Limited testing ratios
������������������� � Indirect Testing � Computer model of a CT to simulate the performance. � Low voltage and currents are applied on the secondary of the CT. � Voltage and currents are measured on the primary loop. � Variety of VA loads, current test points and Power Factors are tested. Good Points: � Light and portable equipment. � Fast and automatic tests. � Can be powered with LV AC source or a 12 V DC car battery. � Unlimited range of CT ratios. � No limit to the current test points. � Wide selection of Power Factors can be used. Bad Points: � Not a traditional testing method (this is changing as more countries and utilities are adopting this method for all the advantages that it has)
�������������������� ������������ � Small & Lightweight (12 Kg), yet tough and durable - Perfect for field testing and convenient for the workshop. � Automatic, fast & fool-proof testing - Reduce testing times and personnel thus lower testing costs. � Safe testing – Less components and safer voltage levels increase safety compared to traditional (primary injection) methods. compared to traditional (primary injection) methods. � Up to 0.2 Class CT testing � 5” screen - Easily see the results in any light condition. � Inbuilt memory - Store up to 100 test results and download them to your computer. � Four terminal test leads - for superior testing accuracy. � Automatic CT demagnetizing after testing . ����� � Live CT ratio test – (HV or LV) With 590F accessory . � CT Error Test – Choice between standard test points . � Full Load VT/PT error test - with 590D-1 accessory . � CT Custom Inject – Input a specific testing point. � 1.6kHz Admittance test � Burden Test � VT/PT ratio test
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