Made from non-tracking material, TE's Raychem Wildlife and Asset Protection portfolio is optimized to ensure tracking resistance, thermal endurance, and UV resistance for high performance protection of your assets throughout their service lifetime. 3. This booklet aims at illustrating the basic criteria needed for good protection of machines and plants in medium voltage networks. The MV primary system voltage and current levels are dangerously high and cannot be connected directly to a relay or meter. ANSI C84.1 defines medium voltage (MV) as being “a class of nominal system voltages greater than 1,000 V and less than 100 kV.” IEEE 141 (the Red Book) references ANSI C84.1 in recognizing the same voltage levels associated with the MV range. 2 Innovative solutions, technology and reliability are ... conductor cables have additional protection in the form of an armor layer. The biggest difference is that medium voltage fuses are not intended to provide overload protection. Medium voltage switchboard system from 1 to 36 kV Sepam Protection relays Masterpact Protection switchgear from 100 to 6300 A A consistent design of offers from Medium Voltage to Low Voltage Guiding tools for more efficient design and implementation of your installations The Guide Design office, consultant, contractor, Transformer MV breakers may include the following protective device numbers: In MV systems, current transformers (CTs) connect protective or metering devices. Due to system operation limitations and equipment selection, selectivity is not always possible for non-emergency or optional standby systems. The RC-Snubber protects the primary windings of a medium voltage transformer from high The APS consists of electrodes nested within each other, which create the power to … Time dial should be set below the transformer damage curve and above the secondary main breaker device. 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. The PCM600 2.10 package includes the following files/documents: PCM600 2.10 Installation Package; PCM600 2.10 Hotfix 20201215; PCM600 2.10 Installation Guide The setting values must be selected above the transient conditions which can occur in the network without requiring disconnection. Our protection relay gives you flexible control to maximize your motor’s output capabilities, and provides current, voltage and motor protection functions. Although the primary windings are rated for MV, the designer must choose either fuses or circuit breakers to protect the transformer. However, for large-scale developments, equipment such as large motors may require a service voltage of 4160 V or higher. As a general rule, 3000 kVA and smaller transformers installed as a stand-alone unit or as unit substations are usually protected by fuses. To see the list of application documents for the product, go to the Specifiers Guide. Click on the desired product type in the Medium Voltage One-line Diagram below to access the detailed product page with product information and publication library links. Magnetizing inrush currents to transformers. 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 protective relay curve only represents the action of a calibrated relay and does not account for the actions of the associated circuit breaker or the accuracy of the current transformers that connect the relay to the monitored circuit. CTs interface the electronic device and the MV primary system. For balanced distribution systems, the ground relay can be set to pick up as little as 25% of load current. The focus of this article is on overcurrent protection requirements for MV transformers, and connecting transformers to common MV distribution systems. NEC Article 490 covers equipment, over 600 V nominal. It is important to note that the overcurrent device on the primary side must be sized based on the transformer’s kVA rating and based on the secondary load to the transformer. NEMA – Medium Voltage Controllers Rated 1501 to 7200V AC ICS (formerly ICS2-324) 5. Medium Voltage Motor & Feeder Protection. The switchboards shall be equipped with two-level ground-fault detection in accordance with NEC Article 517.17(B). acceptance testing, codes and standards, maintenance, medium voltage, neta level 2, neta level 3, neta level 4, protection and control, protective relays, reference guides, relay testing, switchgear, test and measurement, test procedures The main objectives of protection relays are: Identification of the abnormal conditions mentioned is made by the protection relays, which operate to separate the faulty part of the network from the rest of the plant. The installation on neutral grounding resistor should be considered to limit ground fault currents to a safe level for MV generation systems. Medium- Voltage Switching Devices and Switchgear. 7.7 Protection of Distribution Transformers. A satisfactory solution to this problem is the use of extremely inverse relay curves. The utility will include required setting parameters and limitations based on the manufacturer for the protective devices. 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. "For the use of this standard, high voltage (see IEV 601-01-27) is the rated voltage above 1000 V. However, the term medium voltage (see IEV 601-01-28) is commonly used for distribution systems with voltages above 1 kV and generally applied up to and including 52 kV.". For example, Southwire Co. has published tape shields fault current capacity to be 1893 amps at 12.5% tape overlap, and 2045 amps at 25% tape overlap. 8. CTs for protective relaying should be sized 150% to 200% of the full load amperage (FLA). Increasing this setting may restrict feeder coverage or prevent a reasonable setting of upstream or source side fuses and protective relays. In this case an analysis of options must be conducted to determine the best option for the project. Many of these complexes also have high-rise components with MV risers servicing unit substations at strategic locations on multiple levels. 148. Feeder and transformer protection is defined by the applicable equipment standards. Complete guide to protection of medium voltage networks, Electrical Engineering Books and Technical Guides, To provide the operator with an alarm indication under particular network or machine service conditions (for example protection against negative sequence for generators), To put the line or faulty machine out of commission within a short time, as defined in the selectivity study, To carry out automatisms under particular service conditions (for example, undervoltage protections which activate automatic changeover or automatic reclosing of the lines). 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. The purpose of the fuse is to allow for full use of the transformer and to protect the transformer and cables from faults. 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. Article 701.27: Legally Required Standby Systems Coordination. This paper covers general safe operations on Medium Voltage equipment and looks at the aspects of Switching, Isolating, Testing and Earthing, as well Actom Protection & Control INTRODUCTION It is important when operating on Medium Voltage equipment that we follow the safety rules and operating regulations in order to be safe. 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. 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. Most solidly grounded MV distribution system short circuit currents can be well above 10,000 amps. This booklet aims at illustrating the basic criteria needed for good protection of machines and plants in medium voltage networks. 14 3. Device 50 or instantaneous: Set below cable damage curve and must be above the maximum fault current at the breaker total clear curve. Current to raise the temperature of lamps and heater elements. Understand overcurrent protection requirements for medium-voltage distribution transformers. Guide Form Specification RC-Snubber for Transformer Protection 1 General 1.1 This specification is for a _____ kV (line-line voltage) medium voltage three phase metal-enclosed RC-Snubber. A medium voltage fire resistant cable has been developed and tested exceeding existing fire performance requirements. There are three fundamental objectives to overcurrent protection to include ground fault protection: 1. The content is copyrighted to EEP and may not be reproduced on other websites. High inrush current is caused by: Per NEC Art 240.101, the continuous ampere rating of a fuse shall not exceed three times the ampacity of the conductors, and the continuous ampere rating of a breaker shall not exceed six times the ampacity of the conductor. Equipment protection: Protection requirements are met if overcurrent devices are set above load operation levels and below equipment damage curves. 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. However, unless precautions are taken, this setting may be too low to prevent relay misoperation on inrush following an outage. Adequate capacity for the load to be served, Adequate temporary overload capacity (kVA size, or ratings), Primary and secondary voltages properly rated for the electrical distribution system. 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