OLTC Transformer Voltage Bandwidth Regulation
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Solution Overview
Problem
Existing electric power systems with on-load tap changing (OLTC) transformers face frequent tap changes due to variable distributed generation and loads, leading to unnecessary wear and inefficient voltage regulation, especially in systems lacking remote feeder end instrumentation.
Innovation Solution
An electric power system with an OLTC transformer and a processor that dynamically adjusts the voltage bandwidth based on estimated voltage values from downstream buses, using a priori power and current measurements to minimize tap changes and extend transformer life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage bandwidth at the OLTC is continuously adjusted based on worst case assumptions, then the voltage regulation at remote feeder ends is maintained, but the number of tap changing operations increases unnecessarily
Solution Approach 1:
The system performs preliminary estimation of actual bus voltages using a priori power and current measurements before making tap changing decisions. This preliminary action provides more accurate voltage information than worst case assumptions, allowing the control system to avoid unnecessary tap changes while still maintaining voltage regulation reliability at remote feeder ends
Solution Approach 2:
The system uses feedback from measured power and current at the OLTC, combined with a priori values, to continuously estimate the voltage state at downstream buses. This feedback mechanism allows dynamic adjustment of the voltage bandwidth based on actual system conditions rather than static worst case assumptions, reducing unnecessary tap operations while maintaining reliability
2Duration of action of stationary object
If the voltage bandwidth at the OLTC is widened to reduce tap changes, then the service life of the tap changer is extended, but the voltage regulation quality at remote feeder ends deteriorates
Solution Approach 1:
By performing preliminary voltage estimation using measured power and current combined with a priori values, the system obtains accurate information about actual bus voltages. This allows the use of a wider voltage bandwidth without compromising regulation quality, as the control decisions are based on real system state rather than conservative worst case assumptions
Solution Approach 2:
The system dynamically changes the voltage bandwidth parameter based on estimated actual voltages rather than using a fixed conservative range. When voltages are within acceptable limits (determined through estimation), a wider bandwidth is used to reduce tap changes. When voltages approach limits, the bandwidth is tightened to maintain regulation quality, thus extending tap changer life without sacrificing performance
3Reliability
If worst case voltage rises and drops are assumed for all power flow conditions, then voltage regulation margins are maintained, but the voltage bandwidth range is unnecessarily limited
Solution Approach 1:
The system performs preliminary assessment of actual voltage conditions using measured power and current combined with a priori values before applying regulation. This preliminary action replaces blanket worst case assumptions with condition-specific estimates, allowing the voltage bandwidth to adapt to actual system state and expand beyond unnecessarily limited ranges while maintaining adequate regulation margins
Solution Approach 2:
The system makes the voltage bandwidth dynamic rather than static, adjusting it based on estimated actual voltages at downstream buses. This dynamic approach allows the bandwidth to expand when system conditions permit (increasing adaptability) while automatically tightening when regulation margins are at risk, eliminating the need for conservative fixed bandwidth limitations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces unnecessary tap changing operations, providing stable voltage control and extending the service life of tap changers by using accurate network state estimations and additional data like time-of-day and solar profiles to adjust permissible voltage ranges.
Implementation Method 1
An on-load tap changing (OLTC) transformer has several connection points, so called 'taps', along at least one of its windings. With each of these tap positions a certain number of turns is selected. Since the output voltage of the OLTC transformer is determined by the turns ratio of the primary windings versus the secondary windings, the output voltage can be varied by selecting different taps.
Implementation Method 2
Since high voltages are involved, and the taps are changed while the OLTC transformer is under load, each time a tap is changed, arcing occurs. Arcing facilitates deterioration of the associated materials, thereby tending to decrease the service life of the tap changer mechanisms.
Data Source
AI summary
An electric power system includes an OLTC transformer including a plurality of primary and secondary windings inductively coupled to each other. The electric power system includes at least one on-load tap changer coupled to at least one of the primary and secondary windings that is selectively configurable to regulate the portion of the primary and secondary windings inductively coupled to each other. The electric power system also includes a plurality of buses coupled to the transformer and are positioned downstream therefrom. The electric power system further includes at least one processor coupled to the tap changer configured to regulate a voltage bandwidth of the tap changer as a function of estimated voltage values of at least one bus as estimated based on a priori values of power/current transmitted through each bus. The a priori values are substantially based on measured power/current transmission through the on-load tap changer.