Joe Richard 2017-07-15 00:52:12
Facilities with large power usage requirements — 5 megawatts and above — are increasingly implementing power systems that include medium voltage switchgear. From 1,000 to 38,000 volts (V), medium voltage switchgear is often needed for industrial facilities with large motors, chillers or conveyance systems. Medium voltage electrical networks can decrease cabling cost, increase reliability and system redundancy, and provide more control over the cost of power from the utility. However, medium voltage electrical networks also bring a different set of management considerations. Chief among them should always be the safety of personnel and the facility. Dealing with larger, more powerful electrical equipment can feel unfamiliar to many facility managers, but there are some key practices that can be implemented to minimize risk. STRATEGIC DESIGN When designing or expanding a facility, design committees should engage the proper stakeholders, including facility management. At this stage, it is key to express the most important values for received equipment. Important factors include the type of maintenance program in place, and the skill of the operators and maintenance team working with the medium voltage equipment. Teams with highly qualified personnel and an annual maintenance plan may have switchgear that only requires light maintenance. It can include withdrawable circuit breaker switchgear, or large switchgear that trades equipment floor space for more working room in electrical equipment. Facilities less experienced with medium voltage equipment, or that rely on a third party for medium voltage electrical maintenance, would benefit from switchgear that requires less maintenance. New medium voltage switchgear designs can offer sealed or enclosed switchgear that can operate maintenance free for up to 10 years with consistent levels of reliability. This style of switchgear also tends to have a smaller footprint. By using long maintenance interval switchgear, facility managers can reduce safety risks, and place personnel around live electrical equipment less often. New styles of medium voltage switchgear that remove a lot of the traditional risks, such as operational error, access to live components and environmental exposure, are now being introduced to the market. Choosing modern switchgear technology can garner safety benefits unrealized by older designs. ESTABLISHED PROCEDURE Another important part of managing medium voltage switchgear is defining procedures to interact with the existing electrical power equipment. Some questions that should be asked include: • Who should operate medium voltage equipment? • When should the equipment be operated? • Who should be allowed access to the electrical equipment? • Who will be maintaining the medium voltage equipment? Because medium voltage equipment is often used as a backbone for the electrical power network, it is important that its operation is safeguarded from improper access to prevent the risk of an unexpected outage. This can be done by restricting electrical room access to properly trained facilities personnel. Prevention can be accomplished by locking electrical rooms, as well as by padlocking or integral key locking switchgear. In redundant power networks, automated transfer systems switch between sources when required to prevent power outages. Engineered systems such as this help to decrease downtime and respond automatically when an outage is detected. They also eliminate user errors that occur in manual switching procedures, which can happen during the rush to restore facility power. Remote operation via a control room or even a remotely mounted control panel can remove personnel from the electrical equipment during normal operation, as well as prevent inadvertent operation. This can also be a good place to position displays for electrical protection or metering devices. Control of hazardous energy during maintenance should be managed via a well-documented lockout-tagout procedure. This should be established by Occupational Health and Safety Association guidelines, and all maintenance personnel should be trained to follow and comply. RELIABLE EQUIPMENT It is imperative that equipment used in conjunction with electrical switchgear be inventoried and stored in an organized manner. This includes spare parts, personal protective equipment, tags, locks, grounding equipment, metering devices and any other tools that might be used by facilities personnel for maintenance of medium voltage switchgear. Unfortunately, when proper equipment cannot be easily found or accessed, the risk of improper substitution is high. It is important to encourage and enforce proper maintenance procedure through good equipment management. COMPREHENSIVE MAINTENANCE Electrical systems require maintenance to be kept in good working order. It’s just as true for medium voltage equipment. In fact, it could be considered even more critical because medium voltage equipment is frequently used as the main service entrance switchgear or for system redundancy for critical power loads. Facility managers have an obligation to minimize risk of failure of their medium voltage networks to prevent unwanted events that can harm personnel, assets or the business. Proper maintenance can help ensure service continuity, maintain equipment energy efficiency and optimize the total cost of ownership. Reactive versus preventive maintenance Different types of maintenance should be considered according to the criticality of a facility’s medium voltage equipment. Reactive maintenance responds to issues and outages as they appear. It’s main goal is returning equipment to working order, whether through a permanent fix or a temporary solution. This type of maintenance is generally contrary to manufacturer- recommended practices and applicable only in run-to-failure, non-critical designs. Preventive maintenance is a higher level of maintenance practice, and is usually performed on a scheduled basis, including inspection of equipment, cleaning, work on mechanisms and parts replacement. The process also includes diagnostic analysis of equipment to determine the deterioration and life-status. In medium voltage switchgear, these activities can include breaker cycling, conductor inspection and cleaning, bolted connection torque checks, dielectric insulation tests, conductive resistance tests, thermographic scanning, corona discharge scanning and mechanical operation tests. Preventive maintenance extends switchgear life, lowers total cost of ownership of the equipment by reducing unexpected outages and allows for better business decisions in terms of maintenance and replacement. In preventive maintenance practices, the cycle of intervention should receive due consideration. Manufacturers publish recommended maintenance intervals for switchgear that should be followed. Most traditional switchgear has a recommended interval between one and three years. Newer designs have intervals as long as 10 years between scheduled shutdowns for inspection, diagnostics and cleaning. When choosing medium voltage switchgear during design, it is important to consider the maintenance interval impact on total cost of ownership. The perks of predictive maintenance The highest level of maintenance practice in medium voltage switchgear is predictive maintenance. This includes similar diagnostic testing used in preventive maintenance practices, plus the added value of algorithms developed by switchgear manufacturers and maintenance groups used to predict maintenance periods and replacement schedules specific to a facility’s application and environmental conditions. Modern switchgear designs even implement continuous monitoring systems that can analyze temperature, dielectric health, power switching and environmental data. This allows a lifetime view of important factors that can affect the health and stability of a medium voltage power system. These types of systems can be simplified to act like car engine lights, signaling when your system has an issue, so it can be addressed before a failure or outage. This can help prevent issues with personnel or asset safety, and safeguard business impact. It is also important to consider the environmental condition in which the medium voltage equipment is installed and operates. Harsh conditions such as high temperatures, humidity, altitude or intense dust concentration can speed the aging of medium voltage switchgear. In these cases, the frequency of inspection and cleaning should be increased or a condition monitoring system could be implemented. TRAINED PERSONNEL It is imperative that personnel working on or around medium voltage electrical equipment be properly trained and certified. Per the National Fire Protection Agency (NFPA) 70E, a qualified person is “one who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved.” Accordingly, it is critical for facility managers to not only train and certify any personnel that may be maintaining medium voltage switchgear, but also crucial that the training and certification be documented and organized. This allows maintenance schedulers to ensure that only qualified personnel work on the medium voltage power network. Medium voltage electrical switchgear can benefit a power distribution system in terms of increased power delivery and decreased cable and utility costs. When managing medium voltage power switchgear in a facility, it is important to choose the correct switchgear, train personnel, manage procedures and implement a comprehensive maintenance program. This will help reduce risks to the electrical power network, personnel, assets and business. REFERENCES 1) Fulchiron, Didier. 2015. How Medium Voltage Equipment Performance and Reliability Depend on Early Safety Considerations. Doc Ref# 998-2095-12-02-15AR0. 2) Morte, David. 2016. Electrical Distribution Maintenance Fundamentals. Doc Ref# 998-2095-04-28-16AR0. 3) NFPA70E: Standard for Electrical Safety in the Workplace.2012.National Fire Protection Association, Electrical Safety in the Workplace Committee. JOE RICHARD is the United States product launch manager for Schneider Electric’s Premset Switchgear. He graduated from the Georgia Institute of Technology with a bachelor’s degree in electrical engineering in 2007, and has been with Schneider Electric since 2008. Richard has worked in a variety of roles, including sales, marketing and business development, and his main focus has been medium voltage distribution switchgear and its applications. His professional interests include power distribution, energy efficiency, power protection and automation, energy storage and renewable energy.
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