• • • TEST AND MEASUREMENT • • •
immediate or cumulative damage. Mechanical stress, including vibration or physical shock, can lead to structural damage in components, impacting their performance or leading to outright failure. Environmental factors such as moisture or corrosive atmospheres can induce corrosion or create conductive pathways on circuit boards, resulting in failure or degradation of performance. Additionally, manufacturing defects, such as poor soldering, inadequate quality of materials or flawed design, can predispose components or their soldered connections to failure under normal operating conditions. Over time, even natural wear and tear can degrade components, leading to failures as materials fatigue or as tolerances drift beyond operational limits.
Calibration Drift Calibration drift in electronics refers to the gradual deviation of a device’s accuracy from its original output over time. This phenomenon is primarily caused by changes in the physical and electrical properties of the electronic components within the device. Factors such as temperature fluctuations, humidity, mechanical stress and aging of components can alter the electrical characteristics such as resistance, capacitance and inductance, leading to changes in the instrument’s performance. This is particularly important in excitation control systems, as accurate measurements for stator voltage, field voltage, field current, real power and reactive power are essential for proper performance.
Maintaining a regular calibration schedule is crucial to avoid errors in measurements.
electricalengineeringmagazine.co.uk
Calibration drift is not only inevitable but also unpredictable, which underscores the importance of periodic checks and recalibrations to maintain the reliability and accuracy of an excitation control system.
Electrical connections
Degradation of electrical connections in terminals and busbar can significantly impact the performance and reliability of excitation control systems. This deterioration typically results from physical, chemical and environmental stresses. Physical stress may include repeated mechanical movement or vibrations that loosen connections, leading to intermittent or permanent contact failure. Corrosion can also play a major role, as exposure to oxygen, moisture and pollutants can cause the metal components within terminals and
connections to oxidise. This corrosion increases resistance, potentially leading to overheating. Additionally, thermal cycling, where connections are repeatedly exposed to varying temperatures, can cause expansion and contraction of the terminal materials which can result in a loosening of the connection. To mitigate these issues, it is crucial to inspect and check all electrical connections at regular intervals.
A knowledgeable maintenance partner
It is important to partner with a maintenance specialist who understands all the faults covered here, and more, as well as the specific requirements of any given excitation system, regardless of the environments it is in. Excitation Engineering Services’ engineers conduct maintenance work on all types of excitation equipment, from legacy analogue systems to the latest digital ones, ranging in type, size and age. Our maintenance services also cover systems that are no longer covered by OEMs and face obsolescence issues. Typically, maintenance starts with static testing that includes visually inspecting the equipment, secondary injection and calibration checks, relay testing, checking the ancillary components and checking logic circuits.
Dynamic testing is then used to complete the maintenance and verify the performance of the excitation system. This is performed with the generator on open circuit, followed by online testing to assess excitation system performance, including limiters and protective features.
ELECTRICAL ENGINEERING • JULY/AUGUST 2024 33
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
