Explain the detailed function of a sudden pressure relay on a transformer, including its limitations and coordination with other protective devices.

A sudden pressure relay (SPR), also known as a rate-of-rise pressure relay, is a protective device used on oil-filled transformers to detect rapidly increasing pressure inside the transformer tank. This rapid pressure increase is typically caused by internal faults such as arcing or winding shorts, which generate a large amount of gas and heat almost instantaneously. The SPR is designed to react faster than other protective devices to prevent catastrophic failure of the transformer. The relay is typically installed on the transformer tank and is sensitive to the rate of change of pressure rather than the absolute pressure value. It consists of a diaphragm or piston that moves in response to....