33.4
Transformers in Distribution System
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Q1: What is the difference between substation transformers and distribution transformers?
Substation transformers are rated in megavolt-amperes (MVA) and handle high continuous loads with mineral oil insulation and cooling. Distribution transformers step down voltage from primary to secondary systems, are rated in kilovolt-amperes (kVA), and include pole-mounted, padmount, and network types. Distribution transformers connect to secondary distribution networks serving end-users.
Q2: How do load tap changers help regulate voltage in distribution systems?
Load tap changers automatically adjust transformer tap settings to regulate voltage levels based on load variations. This ensures consistent voltage delivery to end-users despite fluctuations in demand, maintaining stable power quality throughout the distribution network without manual intervention or operator adjustment.
Q3: What are the main types of distribution transformers and where are they installed?
Pole-mounted transformers are liquid-filled single or three-phase units used in overhead networks. Padmount transformers are ground-level units that can be liquid-filled or dry-type for underground systems. Network transformers are large liquid-filled three-phase units installed in underground vaults for high-density urban areas.
Q4: Why do substation transformers use mineral oil and inert gas?
Mineral oil provides insulation and cooling for substation transformers. Inert gas like nitrogen fills the space above the oil to prevent oxidation and moisture from entering the transformer, protecting oil quality and extending transformer lifespan by preventing sludge formation and degradation.
Q5: What is the purpose of a conservator tank in outdoor transformers?
A conservator tank manages oil expansion and contraction caused by temperature changes in outdoor transformers. This feature maintains transformer longevity by preventing moisture and sludge formation, ensuring the transformer operates safely and efficiently throughout varying environmental conditions and seasonal temperature fluctuations.
Q6: Can distribution transformers handle loads above their rated capacity?
Oil-filled distribution transformers can handle loads above their kVA ratings for short periods without significantly affecting lifespan due to their long thermal time constant. This allows temporary overload capacity during peak demand while maintaining safe operating conditions and protecting transformer integrity.
Q7: How do transformers contribute to power system distribution reliability?
Transformers step down high transmission voltages to levels suitable for distribution and end-user applications. By regulating voltage through load tap changers and using protective features like pressure-relief diaphragms, transformers ensure safe and efficient power delivery, supporting distribution reliability and automation across the network.