Specialists in HV and MV test and diagnostics. Testing in Substations

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1 Specialists in HV and MV test and diagnostics Testing in Substations

2 Testing in Substations Testing in Substations At 4fores we specialize in the diagnosis and measurement of all types of existing technologies in MV and HV electrical substations where we conduct trials on: Power distribution cables Power Transformers Voltage transformers Current transformers Power Switches Protective relays Faults are pinpointed by performing various tests such as: Prior-location Troubleshooting in cables and / or cable-sheaths Identification of wires Cable routing We have the latest technology in electrical testing for the evaluation and diagnosis of switchgear and electrical equipment in MV and HV installations. Power Distribution Cables At 4fores, we perform diagnostic and troubleshooting tests for electrical distribution cables, using the most up-to-date methods available. The tests are performed both in operating facilities and new ones. We distinguish between two types of tests to conductors according to the desired outcome. The first is for fault-troubleshooting, which focuses on finding and identifying the exact point where the fault occurs. The second type of testing is diagnostic and is, aimed at assessing the state of the cables. Fault Troubleshooting Troubleshooting tests are necessary should any of the following problems arise: Short-circuiting Electrical breaks in cables Resistor failure Intermittent malfunctions Imperfections in cable sheaths Water-tree damage Partial electrical discharge Cable Diagnostics Our diagnostic methodology determines whether the cable is in good working condition, with the minimal voltage being applied to the cable s dielectric. The diagnosis is conducted using two types of test: tan delta and partial discharge: The tangent delta test measures the dissipation factor which, in turn enables one to determine the extent to which the cable has aged or deteriorated. The partial discharge test allows one to ascertain, quickly and reliably, the activity of these discharges and the point at which they occur. The best results are obtained by conducting a symmetric and exactly sinusoidal test-voltage. 4fores performs MV tests in cables, thereby obtaining a thorough understanding of these important elements and their evolution over time. This allows for the anticipation of potential problems in the conductor or in joints and thus allows repairs to be made before a more severe system-failure occurs. Wiring outer cover deteriorated during installation.

3 Testing in Substations Power transformer test and diagnostics. Power Transformers The power transformer is the most expensive element in a substation. The condition-assessment of this is essential to ensure that the substation functions correctly and to ensure that it stays working as long as possible. We test to check the status of the transformer and its ancillary components: Windings Tap-changer Terminals Insulation Core Connection cables Surge arresters We provide equipment to perform the most common tests in the testing of transformers: Static and dynamic winding resistance Ratio and excitation current State of on-load tap changer Leakage reactance Dielectric measurements in terminals Tip-up, tip-down tests Insulationcondition (capacity, power factor/tan δ, dielectric losses) Frequency response tests Analysis of oil degradation Current and/or Voltage Transformers Tests on the current and voltage transformers allow one to detect faults related to wiring and installation prior to use or afterwards. Problems can occur because of faults in the supply itself due to degradation in the accuracy class, shorted-turns, a demagnetized core, degradation of the insulating material, overvoltages and so forth. We conduct the following evaluation tests on voltage and/or current transformers: Relationship of transformation CT or VT load CT excitation curve Checking polarity Testing the accuracy limiting factor Testing power factor. Winding resistance withstand voltage test Power Switches & Breakers. Switches in disrepair can cause electrical arcs, singlephase operation or even fire. In addition, it is necessary to check the insulation periodically as this equipment is subjected to heating from energy created by high-voltages and high-currents; this inevitably affects the insulating material. The most common tests in this type of switchgear are: Contact Resistance Terminals: power factor + insulation capacitance Power Switch: Power Factor Insulating fluids: power factor Operating timen

4 Testing in Substations Protection Systems Protection and control systems play a key role in the safety of both installations and people. For these protections to fulfill their role, it is necessary to define the protection system settings properly and verify that the system is operating correctly. The protection and control systems need to be well-integrated into the substation or power plant to function properly. For this reason it is necessary to check the correct operation of the VT / CT-relay-switch chain. The tasks performed by us which relate to the protection system are as follows: Earthing Network Adequate earthing for a high-voltage electrical system ensures the safety of staff present in the substation. This requires testing to measure step-voltage and touchvoltage while earthed current is supplied, ensuring that the aforementioned do not reach dangerous levels. Earth impedance grounding Measuring the resistance value is the most relevant parameter to test a quality soil system and the ability to perform its function. Step voltage OMICRON relay test set & calibration equipment. Coordination studies: theoretical settings calculation Automatic loading of settings into the relay Secondary injection to verify the correct functioning of any type of relay: Over-current Distance Directional Over-/ under-voltage, etc. It is the difference of potential that a person could experience between their feet with separation of 1 meter, when a fault current appears in a near structure grounded, but with no contact with it. Contact voltage It is the potential difference that a person could experience during a fault that occurs between a grounded metal structure and a point on the ground surface at a distance of 1 meter. Rotary Machinery Rotating machinery is usually exposed to constant stresses and temperature changes that can lead to defects in the insulation, the maintenance of which is key to extending the life of a generator or motor. Resistance of windings Discharge currents Low capacity and/or high frequency Insulation resistance Polarization Index Gis Insulated Switchgear MV gas-insulated (GIS) cells require the completion of a high-voltage resistance test (IEC ) prior to their commissioning. In 4fores we have the means to carry out these tests quickly, thereby reducing the time required to undertake them.

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