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Tap Changers and Smart Intelligent Controls
Published in Leonard L. Grigsby, Electric Power Transformer Engineering, 2017
Dieter Dohnal, Axel Kraemer, Karsten Viereck
The common method of controlling the voltage level of transformers is to equip the transformer with tappings in the winding. The voltage variation will be achieved by changing the turn ratio. The tap changer changes the ratio of a transformer by adding turns to or subtracting turns from either the primary or the secondary winding. Therefore, the transformer is equipped with a so-called regulating or tap winding that is connected to the tap changer. The execution of a tap-change operation with a tap changer can be done with the transformer de-energized, when tap-changing is required rare, or it can be done with the transformer energized that means on-load. For these different demands, de-energized tap changers or on-load tap changers are used, controlled by intelligent regulating devices.
Interconnecting Electric Generators
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Voltage is adjusted by the utility using load tap changers or induction voltage regulators. A load tap changer is a motor-driven switching device that can adjust transformer ratio in response to voltage variation. A voltage regulator is an automatic transformer connected in series with the main transformer. Capacitors that can be switched in and out of the circuit are used to control voltage changes resulting from PF variations. Figure 28-5 illustrates a primary distribution feeder with step voltage regulator and voltage profile.
Design, Construction, and Operation of Distribution Systems, MV Networks
Published in James Northcote-Green, Robert Wilson, Control and Automation of Electrical Power Distribution Systems, 2017
James Northcote-Green, Robert Wilson
Voltage Control by the Distribution Transformer Tap Changer. Distribution transformers up to a value of typically 1000 kVA can be fitted with a tap changer, although it is normally an off load device. Five taps, with ratios of –5%, –2.5%, nominal, +2.5% and +5%, are common. This tap changer is used to provide a basic control over the voltage on the LV side of the transformer, where the loads may still vary considerably over time, but where the on load tap changer would be too expensive.
Voltage Regulation Planning Based on Optimal Grid-Connected Renewable Energy Allocation Using Nature-Inspired Algorithms to Reduce Switching Cycles of On-Load Tap Changing Transformer
Published in Electric Power Components and Systems, 2023
Hamid K. Ali, Ahmed M. A. Haidar, Norhuzaimin Julai, Andreas Helwig
The on-load tap changer as shown in Figure 1 is a device used to regulate voltage by rewiring a winding to make it appropriate for functioning while the transformer is energized and loaded. The oil tank of the tap changer mechanism attached to the transformer contains connection points of variable turn ratios that can be selected in distinct steps. The downstream bus voltage of the transformer is adjusted by selecting the ideal tap position which takes about two to ten seconds to change the tap position. The inherent tap positions of the OLTC are often consistent across manufacturers’ equipment. Increasing the tap position results in rising the number of primary turns, which increases the transformer’s secondary voltage and hence the downstream voltage. The downstream voltage is lowered by decreasing the tap position. If the bus voltages remain within allowable operating limits, the generators, transformers, and reactive sources of power in the system can satisfy the kVAr load requirement [44]. However, when the bus is heavily loaded, the bus voltage may exceed the permitted voltage band limit, forcing the tap to change frequently its position to keep constant bus voltage levels. The voltage at the effective turns ratio of the OLTC can be expressed as in (1) with the defined transformer taps operation limit [31, 45, 46]. Where and are the lower and upper voltage boundaries, is the desired voltage level. Normally, in the power transformer, the forward/backward switch of OLTC enables 10% of the regulation range in 16 steps up and 16 steps down, which is about “” per unit change at each step [47].