medium voltage protection guide

“Some people consider anything above 1000 V as high voltage. Ampacity of MV conductors feeding to and extending from the transformer, as well as necessary overcurrent protection of the conductors and equipment, are covered under the following: Cold load pickup is defined as follows: Whenever a service has been interrupted to a distribution feeder for 20 minutes or more, it may be extremely difficult to re-energize the load without causing protective relays or fuses to operate. To accomplish this, the fuse curve should be to the right of the transformer inrush point and to the left of the cable damage curve. Selection of the protection system and relays depends on and is correlated with the plant characteristics, type of indus-trial process and its service continuity requirements, with the status of the neutral, characteristics of the machines, levels and duration of the fault currents, etc. To be clear, a properly sized and rated transformer includes the following features: The 2011 NEC requires that transformers be protected against overcurrent (NEC Article 450.3). NEC Article 310.10 requires shield MV cable for distribution above 2000 V. NEC Article 490.46 MV circuit breaker shall be capable of being lock-out or if installed in a draw-out mechanism, the mechanism shall be capable of being locked. The protection relays are normally provided for different objectives and aims! In distribution design, the three objectives still apply: For example, if the NEC requirements for transformer overcurrent protection are considered without reference to applicable standards and code requirements, the system may address protection of transformers, while other elements of the distribution system (such as the feeders connecting the transformer(s) to the distribution system) may not be protected in accordance with the code. Figure 4 Figure 5 Figure 6. The input for a distribution substation is typically at least two transmission or subtransmission lines. They should only be applied in situations where industrial substations. Settings do not correspond to those listed as standard in the NEC [NEC Article 240-6(a)]. Understand overcurrent requirements for medium-voltage distribution. Another feature of large commercial complexes is the associated central plant function with MV chillers and unit substations. Search Products And Discover New Innovations In Your Industry, i. This form of protection employs relays with inverse time-current characteristics; that is, operating time of these relays becomes less as the current magnitude increases. A sample of a few of the protective function numbers that are used in this standard are shown in Table 1. CTs for protective relaying should be sized 150% to 200% of the full load amperage (FLA). In general, higher service voltage results in more equipment expense. CxEnergy and the AABC Commissioning Group (ACG), By Leslie Fernandez, PE, LEED AP, JBA Consulting Engineers, Las Vegas, Medium-voltage breaker switchgear example (800 amp service), Medium-voltage breaker switchgear example (oil-filled power transformer), Understanding changing data center metrics, Ultra-low temperature storage considerations for COVID-19 vaccines, Case study: University science building control systems, Neurologic institute building trying to redefine patient care, Video: Commissioning for Reliability and Resiliency – Lessons Learned, How advanced digital twin technology narrows the industrial skills gap. This booklet aims at illustrating the basic criteria needed for good protection of machines and plants in medium voltage networks. Medium- Voltage Switching Devices and Switchgear. The medium voltage quality system has been certified as being fully compliant with the requirements of the ISO 9001:2015 quality assurance model. MV breaker protections are used for transformer sizes greater than 3000 kVA. High-voltage power fuses provide a reliable and economical means of protecting small to medium-sized CE – European Directives for Safety and EMC 4. The ground fault relay or sensor must be set to pick up ground faults that are 1200 amps or more and actuate the main switch or circuit breaker to disconnect all ungrounded conductors of the faulted circuit at a maximum of 1 s. For hospitals, the substation feeding the distribution system is typically liquid-filled MV primary to 480/277 V secondary transformers connected to service switchboards with both main and feeder breakers. When connecting to an existing utility, the utility typically directs the interconnection requirements including protective device requirements. Selection of the protection system and relays depends on and is correlated with the plant characteristics, type of industrial process and its service continuity requirements, with the status of the neutral, characteristics of the machines, levels and duration of the fault currents, etc. 134. Under a fault condition, the fault current can easily exceed the capacity of the cable tape shield or concentric neutral ground; hence, a separate ground wire is necessary. Each product is backed by an efficient worldwide distribution network with unrivaled service and technical support. Current to raise the temperature of lamps and heater elements. 15 • Outdoor medium voltage padmounted switchgear - … He has more than 28 years of engineering and design and field experience that includes MV distribution systems for military, mining, tunneling, food manufacturing, power production facilities, high-rise facilities, and casino resort complexes. It is important to underline at once that trip selectivity must always be looked for, but must only be looked for after having ensured protection of the network component. Until recently, engineers didn’t work too frequently in the design of medium-voltage (MV) systems, mainly because anything over 600 V was primarily handled by the utilities. Eaton’s dry type transformer solutions are custom-designed dry-type power transformers, which give environmental protection, for both indoor and outdoor applications. Operation levels and below equipment damage curves is defined by the application have fixed trip ground-fault selectivity problem the. Situations where a medium voltage power Conversion equipment Preliminary standard 2 a stand-alone unit or as substations. 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