66kv Transformer Fault Analysis For a 66kV transformer secondary winding deformation fault case, we elaborated
An electrical transformer an electrical static energy converter that transfers electrical energy , without altering its frequency. The transformer electrical is a massive and significant piece of electrical equipment that is part of the power system. The capability of this transformer is about 9 times greater than the power for the generator. Its role is to increase or decrease the voltage of electrical energy within the power system to enable the efficient distribution, transmission and use of electrical energy.
Within the power system the more voltage is higher the lower the current, and the less power loss that occurs on the transmission line. Additionally, the area of the cross-sectional transmission line is also decreased, which decreases the amount of metal that is used to make the cable.
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An electrical transformer’s central core has to be grounded at a specific place in regular operation. If there is no grounded the core, the voltage that is suspended from the core to the ground could result in an intermittent discharge from the core to the ground. the grounding of the core will eliminate the risk of creating a suspended voltage in the center.
But, if you ground the center more than two points the uneven potential between cores can form an arc current between the points of grounding and create the multi-point grounding to heat defect within the core.
The fault in the grounding of the electric transformer’s core could result in the core local overheating. This can be serious, causing the core’s local temperature to rise as well as light gas movement and may even trigger massive gas action and even a the possibility of tripping accidents.
The melting part of iron’s core causes the short circuit fault in the iron chip leading to a greater loss of iron and impacting the performance and functioning that occurs in the electric transformer, to the extent that the core of the iron is required to be replaced to fix the issue.
This is the reason why transformer electric is not able to allow multi-point earthing . It is only provides one spot for earthing.
The cores of most electrical transformers are composed of silicon. It is one form of steel that has 0.8 to 4.8 percent silicon (also called silicon). Silicon steel is utilized as the primary component of transformers because it is a magnet that has a high permeability.
This allows it to generate huge magnetic inductions in an energized coil, thereby permitting the transformer to shrink in dimensions.
As we all know, the real Transformer electric always operates in AC, and the power loss does not just occur due to the resistivity of the coil they also occur within the core due to magnetic alternating. The power loss that occurs in the core is often referred to as “iron loss” that is caused by two elements: “hysteresis loss” and “eddy current loss”.
Hysteresis loss is the loss caused by the existence of hysteresis inside the core of the transformer during the process of magnetisation, the magnitude of this losses is in proportion to the area that is enclosed by the line of hysteresis in the material. The hysteresis lines of silicon steel is very narrow, which means that the hysteresis loss of the transformer’s core is minimal and heat generated is significantly decreased.
Because silicon steel has all the advantages mentioned above so why not use the entire silicon steel as the base and also for converting it into sheets?
This is due to the fact that the core iron sheet helps reduce another form of loss to iron – “eddy losses in current”. In the event that a transformer operation there is an alternating current inside the coil. The magnetic flux that it generates is, of course, changing.
The fluctuating flux creates an induced voltage in the core. The induced current within the core circulates in a plane that is perpendicular to the direction of magnetic flux, which is why it’s the term eddy current. Eddy current losses can cause the core to heat.
In order to minimize losses from eddy current in the electric transformer is laminated with steel plates made of silicon that are separated from one another, so that the eddy current runs in a narrow path through smaller cross-sections to increase the resistance of the path of the current while at the same the silicon contained within the steel enhances the material’s resistance and helps in reducing the amount of eddy current.
The transformer’s core is usually made of 0.35mm thick cold-rolled silicon steel. The steel can be cut in long pieces that are sized according to the dimensions of the core that is required. They are then formed into an “sun” shape or “mouth” form. From the standpoint of logic, if you want to decrease eddy current, the less thick the silicon steel sheet, the smaller the spliced piece is, the more effective. This does not just reduce the loss of eddy-current, but also it also reduces the temperature rise but also preserves that sheet of silicon material.
However, in practice in the real world, it’s not easy to create silicon steel cores, it is possible to make silicon steel. Not just from the previously mentioned side of positive aspects, but also because it allows the manufacturing process of the core can significantly increase the amount of hours it takes, but as well to decrease the cross-sectional area for the entire core. When making cores for transformers using silicon steel sheets, it is important to begin with the particular situation by weighing all the benefits and drawbacks and select the appropriate size.
1.) Short circuits with multiple phases within the Electrical transformer.
2.) Short-circuits between turns, and housing or core.
3.) Iron core that is faulty.
4.) Lowering the oil level could cause result in leakage of oil.
5) Tap changer contacts that are not as good or wires with poor welding.
1. The main protective transformer is constructed and designed following the principles of circulating current. it is manufactured and designed in accordance with the properties of the internal faults in the transformer. is able to produce or break down gas.
2, Differential Protection is the primary protection for the transformer, whereas gas protection is the main safeguard for the transformer in the case of internal failures.
3. Differential protection in accordance with the protection’s scope.
1)Multi-phase short circuits occur in the main lead-in line for transformers and in the transformer coil.
2)Serious single-phase inter-turn short circuit.
3)Earthing fault in the lead-in and protection coil line of a high-current earthing system.
1.) A multi-phase short-circuit within the transformer.
2.) A short circuit in between the turns between turns, as well as the outside or core as well as short circuit.
3.) A fault inside the iron core (heating or burning).
4.) Lowering the oil level could cause result in leakage of oil.
5) A poor tap changer connection and poor welding.
1. When the section cooler I, II of the power loss is triggered, it will issue a “#1, #2 Power failure” warning, then the main electrical transformer circuit that is full stop tripping will immediately notify to the dispatcher, and then disable the protection set.
2. If the switching of the power supply in sections I and II fail to the operation “cooler fully stop” will be illuminated after which the complete stop-tripping circuit central coolers will turn on. The protection set should be immediately reported to dispatch and then deactivated immediately. Manual switch must be done immediately.
3. If one of the cooler circuits fails Then, you must isolate the malfunctioning circuit.
When different ratios of transformers are run in parallel, they’ll create circulating currents, which can alter how the power of the transformer is generated. In the event that the electrical groups aren’t identical, and the two transformers are operating in parallel, this could cause the transformer to short circuit.
3.) A poor internal connection and discharge fire.
4.) Remove individual parts.
5.) Short or grounding circuits within the system.
5) The motor’s large start-ups cause the load to change massive.
In what circumstances is it prohibited to change the on-load-tap-changer that is part of the transformer?
1) When it is the case that the transformer electrical overload is operating (except in certain circumstances)
2.) If it is the case, the protection for light gases of an on-load regulator often indicated.
3.) In the event that there is no petroleum in the marking on the regulator for on-load.
4)When it is determined that the total number of regulatory units are greater than the number specified.
(5) In the event that an anomaly occurs within the regulator.
This rating is the specifications of the manufacturer for normal usage for the unit. The transformer is operated at the specified rate for long-term stability and high performance. The rating includes the following factors.
1. Rated capacity is the transformer operating in the rated condition of the output capacity that is guaranteed to be that is, the unit that has the volt-amperes (VA) and the kilovolt-amperes (kVA) and megavolt-amperes (MVA) due to the fact that the transformer is very efficient operating efficiency, it is usually the original reverse winding, of design value is equal.
2. Rated voltage is the transformer’s no-load ending voltage guarantee, the unit that has voltage (V) and Kilovolts (kV) stated. If there are no instructions specific to the transformer are given, the term “rated voltage” refers to the voltage of the line.
3. Rated current is the term used to describe the capacity and the voltage calculated rated line current, also known as the device with the ampere (A) mentioned.
4. No-load current: transformer operation with no load that is the current of excitation in percentage of the current rated.
5, short-circuit loss one end of the winding short circuit and the other end of the voltage is applied on both ends of the winding in order to reach the nominal current of the active loss. The unit is in the watts (W) or Kilowatts (kW) described.
6. No-load loss is the transformer that operates in non-load operation in the power loss that is active. That is, the unit in the watts (W) or Kilowatts (kW) is used.
7. Short-circuit voltage, Also known as impedance, refers to a shorter circuit that runs on one side of the winding and the opposite side to get to the maximum current when voltage is applied and the proportion of the rated voltage.
8. Connection group is the indication of the connection between two windings, the main and the second, and the difference in phase between the line voltage expressed in clocks.
Electrical transformers are typically intended for rated capacity and not for rated power since the current is connected to the rated capacity. In the case of voltage source inverters, the capacity rated is close to that of the power that is rated since the power factor of the input is nearly 1.
It’s not the same for inverters that use current sources, whose the input side electric transformer power factor is about equivalent to that of the motor that is used to load and, therefore, for the same motor, its capacity is slightly higher in comparison to a voltage source inverter transformer.
The voltage influences the choice of a core, and the choice of conductor’s type is tied to current. i.e., the size of the conductor is directly proportional in proportion to the heat produced. That is, the performance that a transformer has is proportional to the amount of heat produced.
If a transformer is well-designed and that is operating in an area with inadequate heat dissipation, it has a capacity of 1000 KVA and can run at 1250 KVA if the capacity for heat dissipation is enhanced.
Additionally, the capacity nominally of the Transformer electric is also related to the maximum temperature rise that is permissible. For instance, the 1000 KVA transformer has the proper temperature increase of 100 K, is permitted to operate at 120 degrees in certain conditions, and has an output greater than 1000 kV.
It is also evident that when the thermal condition of the transformer is improved, the capacity of the transformer can be increased. Consequently, the size of the cabinet is reduced to the same capacity as the inverter.
1.) Use low-loss, energy-efficient transformers.
2.) Choose a transformer with an adequate capacity in line with the load conditions
3.) The charge factor must be greater than 70%.
4.) When the load factor is usually less than 30 percent, the transformer must be replaced by a smaller capacity electrical transformer if needed.
5)Improve the power factor of the load to improve the ability of the transformer to supply active power
6.) Make the load configurable and limit the number of electrical transformer units operating.
The high energy use of transformer electrical mainly refers to SJ, SJL, S7, S7, and other series of electric transformers. Their copper loss and iron loss are significantly more than the popular S9 series of transformers for electrical use. For instance, the S7 in comparison to S9, where iron loss is 11% more and losses in copper is 28% more. It is also more costly. S7 has 11% more in terms of loss of iron and 28% greater loss of copper than S9.
The latest transformers, including the S10 and the S10 as well as the S11 Electrical transformers, are more efficient than the S9, and the loss of iron from the Amorphous alloy transformer electrical is only 20 percent less than the S7.
The majority of electric transformers have a lifespan of many decades. The replacement of a large energy consumption electric transformer with an energy-efficient electric transformer not only enhances the efficiency of the conversion process and also leads to a significant reduction in energy consumption over the transformer’s lifespan.
If an AC flows through the conductor, it creates an alternating magnetic field that is created within the conductor. The alternating magnetic field creates an induced electric current inside the conductor in its entirety. This is known as eddy-current because it creates an enclosed loop within the entire conductor, similar to a vortex in the water.
Eddy currents do not just cause the loss of electrical energy without cause and can cause electrical devices (e.g., transformers) to become hotter and, in extreme cases, could affect the operation of the machine.
This is to take into account the quality of the protection relay. High-voltage side quick-break protection can be a dangerous safeguards Transformer electric external faults. In the rectification, it is not meant to protect from the electric transformer low-voltage side of the most intense short-circuit current because of the low-voltage aspect of a short-circuit range with currents that are not too far from the outlet, which is identical, which can cause the high-voltage part of the quick-break range to extend to the low voltage outlet, which means that it loses selection.
Following the removal of selectivity protection, it is more reliable, but it is also to let the inconvenience pass. For instance, the availability of industrial round sets 10KV total distribution rooms (10KV bus and outlet circuit breakers). Each workshop has set up a distribution room with low voltage (ring network cabinet and transformer). In the event that the circuit breaker fails to get out of the transformer’s low voltage portion of its maximum short circuit current, it can cause the complete low-voltage switch (ring load switch in the network cabinet fuse) high-voltage circuit breaker action to be activated. This could result in disruption of the operations.
In high-current systems, to satisfy the requirements of protection relay sensitiveness, one component that is the primary electrical transformer must be grounded, and the other one uncovered.
Two primary electrical transformers in an electrical station are not grounded on neutral points simultaneously due to the coordination of zero sequence of currents and voltage protection.
In substations that have multiple transformers that operate in parallel, it’s typical to work with one component of the transformer having a neutral point grounded and the other without.
This reduces the amount of the earth fault voltage to a sensible range and also makes the scale and steps of the Zero Sequence current of the grid inscrutable through changes in operating mode and increasing the sensitivity of the Zero Sequence Current Protection.
Disconnecting an unloaded electric transformer operating within the grid can result in an overvoltage operation. In earthed systems with low-current, the amount of overvoltage may be between 3 and four times the voltage of the phase.
In larger earthed systems, the operating voltage can be 3 times the phase voltage.
To verify that the transformer’s insulation can stand up to the voltage that is rated and operating overvoltage during the course of operation, various tests of impact closure are performed before the transformer is put in process.
Furthermore, when the transformer goes in no-load mode, there is an inrush current generated, up to 6-8 times the current rating.
Because the excitation inrush current may generate lots of electromotive force, it is nonetheless a sensible way to evaluate the power of the electric transformer and whether the relay protection system is functioning correctly.
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