Applications of Optical instrument transformers for protection and control include: Transformer protection and Excitation (Volts / Hz) Line protection (Transmission & Distribution) Phasors Generator Protection Undervoltage loadshedding Reactive Devices such as shunt and series capacitors (we may add bus protection) Applications can start with where precision in measurements are more suited such as undervoltage load shedding, or where the need for redundancy or the requirements for coordination with other schemes are inherent to the overall protection application. For instance, the voltage input for a transformer overexcitation protection can be supplied using Optical voltage transformer. In this example, there are other protection systems that provide some level of overlapping protection in the absence of voltage, and while the alarms due to loss of voltage alert the need for maintenance. Another example in transformer protection is use of optical current and voltage instrument transformers when loss of current or voltage only disables partial protection. In the case of line protection utilizing power line carrier protection, provisions for stand alone external coupling capacitor voltage transformer is needed as the optical instrument transformers do not provide the coupling voltage transformer. Also, in line protection applications utilizing distance or directional overcurrent protection, the need for dual secondary winding is more evident. In applications when both current and voltage inputs are needed, it may be best to apply optical CT / PT with necessary hardware to support the protection and control equipment. (details?) Some of the more precise applications such as Phasor Measurement will benefit from the optical instrument transformers. When streaming data from such device to a PDC, the user will need to be aware of data from the Optical sources vs. conventional instrument transformers. Another key consideration in Optical technology application is backward compatibility and ease of upgrade where the electronics (or amplifiers if applicable) used in conjunction with the primary measurement devices need to be easily upgradable or backward compatible as technological advancements makes existing installations of obsolete or parts become unavailable. Application considerations also include the types of problems incurred in installation, commission test procedures, and during normal operation. For example, the need for maintenance tools; i.e: ways to measure leakage, alarm types, alarm set-points, and criteria for alarm set point derivation and ways to verify alarm set points during commission testing are amongst considerations when installing optical technology.
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