IEEE PES SPDC Working Group 3.6.13

Smart Grid Surge Protection Devices Whitepaper

DRAFT May2013

Note: Yellow Highlighted text were added during the WG meeting

SUMMARY

This paper has presented a brief overview of the surges which occur in ac power, control and communication circuits, and the use of surge protective devices to mitigate these effects. An overview of pertinent industry standards is provided. The objective of the IEEE/PES/SPDC WG 3.6.13 is to develop an application guide for surge protection of the North American Smart Grid. This will serve to assist the industry at large with a guide for best practices in identifying locations where the application of surge protection needs to be considered and how to determine the specification and selection of these devices. [ARM1]

1.0 INTRODUCTION AND PURPOSE

The purpose of this paper is to outline how surge protective devices play an integral part in improving the operability and reliability of the North American Smart Grid and its components. This paperfocuses on surge protective devices (SPDs) that operate on systems up to 1000V AC or 1500V DC. Applications include connection to power equipment, as well as data and signaling circuits for control, monitoring and communication. The selection and application of surge protective devices based on transient exposure levels are discussed.

2.0SMART GRID

2.1 Smart Grid Overview

The basic concept of Smart Grid is to provide interoperability of the national electrical delivery system by means of monitoring, information, control, and communication capabilitiesto the national electrical delivery system to maximize the reliability of the system while reducing the energy consumption. The Smart Grid will allow utilities to transmit and distribute electricity throughout the system efficientlythrough the deployment and use of intelligent electronic equipment in thesub-domains associated with the electric power and the public and private communications.This will allow homeowners, businesses and industrial facilities to use electricity more intelligently.

2.2 Smart Grid and Communications

Protection of the communication linksfrom overvoltagedisturbances are important in aSmart Grid since operation depends upon a reliable two-way communication between the electric utility and the customer for effective service. This may be as simple as providing information to the customer about the cost of the power he is using; or it may directly control equipment within the facilityso as to manage peak power demand from the grid.

Communicationstypicallyemploy wireless,power line carrier, copper or fiber-optic services. The service needs to be interfaced to a network. Generally this interface is implemented by a box called a gateway, which is located where the communications service enters the structure. A prevalent myth is that if this gateway is served by a fiber optic or wireless connection, it is immune from damage by lightning. Howeverthis may not be the case, as will be shown in the lightning section of this paper,

Figure 1. A typical home network consisting of electronic equipment connected to a gateway via an Ethernet link add w-m meter with radio wave graphics

2.3 Importance of Surge Protection for Smart Grid

Key aspects of Smart Grid point to an increased need for surge protection due to:

  1. Addition of electronic based monitoring, analysis, control and communication equipment. – Surge protection is required to protect this electronic equipment from damage due to voltage transients.
  2. Proliferation of communications, control and monitoring devices and the addition of distributed and alternative power sources, increases the exposure of equipment to lightning and other surges.
  3. Increase in residential, commercial and industrial use of energy management systems and distributed generation cause more switching of loads and generation sources within the premise; thereby increasing the need for point-of-use protection inside the premise.
  4. The overall geographical reach of the Smart Grid poses an increasedexposure to lightning damage or disruption. This risk is proportional to the lightning strike density and capture area of the grid.

Manufacturers of electronic equipment / appliances areSOMETIMESrequired to meet certain EMC requirements[JLK2] which include minimal surge withstand levels. Examples include: EN61000-6-1 (EMC Immunity for Residential, Commercial and Light Industrial Environment) and EN61000-6-2 (EMC Immunity for Industrial Environments)

Internal protection installed in equipment may not be adequate for the exposure of the electrical environment in which the equipment is installed. Consequently, additional surge protection may be required.

WHO REQUIRES THESE?

Distributed generation systems found in the smart grid often utilize power inverters and electronic controls which are susceptible to damage from Overvoltage and as such require surge protection on both the output (AC) and input (DC) to protect the sensitiveinternalelectronics.Along with protecting thisutility equipment, the customer equipment must also be protected.

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Voltage surges and impulses can be internally orexternallygenerated and only a well designed protection system will enhancesystem reliability.Surge Protective Devices are a necessary part of the commercial, industrial andresidential power distribution system landscape. Whether incorporating a surge panel, asurge strip or a distributed system including a panel, sub-panel and point of usedevice, surge protection provides valuable down line protection from damage due tosurges on the power lines.

3.0ELECTRICAL DISTURBANCES AND SURGES

Surges are brief overvoltageswitha time domainin the microsecond to millisecond range, and can be superimposed onto a power and/or communication system. They can upset or damage electronic equipment within a facility, since they can reach amplitudes of tens of thousands of volts.

3.1 Internally Generated Disturbances

Surge disturbances can originate inside or outside a facility. It is estimated that 60 – 80% are internally generated within the facility. A common source of these internalsurges are devices that switch power. This can be anything from a simple thermostat switch operating a heating element to a switch-mode power supply found in many electronic devices.Examples of switching surges include:

Contactor, relay, and breaker operations. These devices include inductance which stores energy that may be released as anarc across the contacts when switched. The waveform of these surges is often complex with amplitudes that may beseveral times greater than the nominal system voltage.

Switching of capacitor banks. Capacitor banks are commonly used to manage power factor correction within the facility’selectrical system. These capacitor banks are switched into and out of operationto regulate the reactive power. Thisswitching action can create ringing, with voltage amplitudesthat may beas high as four times the nominal system voltage

Switching of inductive devices. Another common source of switching transients is the discharge of inductive devices. Examples of this include the discharge of energy stored in transformers, reactors and motors. These devices store energy during normal operation, which when switchedis released into the electrical system.

3.2 Lightning Disturbances

Lightning protection systems (LPS) can improve the reliability of the electric power and the communication systems.The design of a LPS is based on statistical information related to the ground flash density (isokeraunic maps) and the location of the structure. The effectiveness of the LPSrelies on correct grounding (earthing) and bonding methods. Not all facilities require or need to have the same degree of lightning protection.

During a lightning discharge, the passage of the direct lightning current from the lightning receptors (or any other air terminal) at the top of the structure to ground via the LPS down conductors, may induce overvoltages into the internal wiring system when these conductors are within approximately10 meters of each other.

3.3 Other line-side disturbances

Many of the internally generated surges discussed earlier are similar to those present on the line side of anyservice entrance equipment of a facility. There is a major difference, however, between internally generated surges within a facility and those propagating into a facility from the line-side. Any outside power source connected by metallic conductors may be a point of entry for other line side voltage or current surges. This difference is generally in the amplitude of the surge. The surges from the line sideare typically much higher in amplitude from the surges generated on the load side. Line side surges are generally associated with equipment damage while load side surges are more commonly associated with equipment upset.

The surge environment is well discussed in IEEE Std. C62.41.1™ IEEE Guide on the Surge Environment in Low-Voltage (1000 V and Less) AC Power Circuits. This includes line-side and load-side surges. IEEE Std. C62.41.2™ IEEE Recommended Practice on Characterization of Surges in Low-Voltage (1000 V and Less) AC Power Circuits presents recommendations on the selection of representative surge parameters to be considered in assessing equipment immunity and performance of SPDs. The contents of these two documents address the majority of surge issues that smart grid products and equipment are exposed to.

Note: The application of surge protective devices to phenomenon such as electromagnetic pulse (EMP) disturbances and geomagnetic disturbances are not covered. which are generally associated with solar flares and the magnetic fields that result in large dc offsets between geographical regions of the earth’s surface. These voltage differences drive currents through the electric power and communications systems.

4.0SURGE PROTECTION

4.1 Overview of Surge Protection

A Surge Protective Device (SPD) is a device that protects electrical and electronic equipment from the damaging effects of voltage transients. This protection is typically accomplished by diverting surge current,thereby reducing the level of the voltage transients. These devices are employed to protect electrical and electronic loads or the facility’s service equipment.

When a voltage transient appears on the system, the SPD changes state from being very high impedance and drawing little to no current, to a low impedance state where excess current is diverted and the SPD limits the voltage.If correctly selected, coordinated and installed this SPD will protect the downstream equipment. A second important function of an SPD is the ability to equalize or reduce voltage differences that occur across grounded and bonded components of the power and communications systems.

Examples of components used in SPDs are: metal oxide varistors(MOV), thermally-protected MOVs, avalanche breakdown diodes (ABD), [JLK3]gas discharge tubes (GDT),passive filters and circuits including combination designs of these components. In addition, communication circuits might use Electronic Current Limiters (ECL) and/or Positive Temperature Coefficient (PTC) devices.Inductors and/or capacitors may also be included to provide filtering.These devices mitigate surge voltage impressed on the protected equipment, but they also reflect part of the surge voltage back to the source, thus increasing the stress imposed on the up stream side of the point of installation of these devices.

4.2 Assessment Process to Determine Proper Surge Protection for Different Facilities and Equipment

TheInstitute of Electrical and Electronics Engineers (IEEE) developed INSERT FULL TITLE of Recommended Practice, C62.41.2-2002 as an electrical transient exposure level/surge severity categorization guideline. These severity levels enable manufacturers to test and users to specify the appropriate protection level based on one of three Categories. The categories include outdoor location, service entrance equipment and inside the facility.

INSERT GRAPHIC OF CATEGROY LOCATIONS

IEEE Category C / High /
  • Service equipment
  • Service entrance near utility substation
  • Service entrance on grid with other large industrial users

IEEE Category C/B / High-to-Medium /
  • Service entrance remotely located from utility power factor correction and grid switching
  • High-lightning area distribution panels feeding roof-top loads

IEEE Category B / Medium /
  • Large distribution panels
  • Non-service entrance distribution switchboards
  • Heavy equipment located near unprotected service entrance
  • Panels feeding variable speed drives
  • Non-service entrance motor control centers utilizing drives, PLCs, soft-start or electronic starters

IEEE Category B/A / Medium-to-Low /
  • Branch panels with heavy sensitive equipment loads
  • Branch panels with combination of "dirty" and sensitive loads
  • Branch panels without up-stream protection
  • Busway feeding sensitive loads
  • Bus riser feeding multiple floors with critical or sensitive loads

IEEE Category A / Low /
  • Branch panels with upstream protection
  • Branch panels with primarily sensitive electronic loading
  • Branch panels deep within a facility

Add Table of waveforms and graphic ABC

5.0EXISTING STANDARDS AND RESOURCES

5.1 SPD Related Standards

There are a number of industry standards that apply to surge protective devices (SPDs), whether they are connected to the electrical system through a plug-in connection or hard-wired connection to the facility wiring.These include:

IEEE C62.41.1 (2002): Guide on the Surge Environment in Low-Voltage (1000V and less) AC Power Circuits - This guide provides comprehensive information on surges and the environment in which they occur. It describes the surge voltage, surge current, and temporary overvoltages (TOV) environment in low-voltage (up to 1000V root mean square [RMS]) AC power circuits. It is a reference for the second document, which describes the surge environment.

IEEE C62.41.2 (2002): Recommended Practice on Characterization of Surges in Low-Voltage (1000 V and less) AC Power Circuits - This guide presents recommendations for selecting surge waveforms and the amplitudes of surge voltages and currents used to evaluate equipment immunity and performance of SPDs. Its recommendations are based on the location within a facility, power line impedance to the surge, total wire length, proximity, and type of electrical loads, wiring quality, and more.

IEEE C62.45: Recommended Practice on Surge Testing for Equipment Connected to Low-Voltage (1000V and Less) AC Power Circuits - This guide focuses on surge testing procedures using simplified waveform representations (described in IEEE C62.41.2) to obtain reliable measurements and enhance operator safety. This guide provides background information that helps determine whether equipment or a circuit can adequately withstand surges.

C62.43-2005 Application of Surge Protectors Used in Low-Voltage (Equal to or Less than 1000 V, rms, or 1200 V, DC) Data, Communications, and Signaling Circuits

C62.72-2007 IEEE Guide for the Application of Surge-Protective Devices for Low-Voltage (1000 V or Less) AC Power Circuits

National Electrical Code (NEC) and National Fire Protection Association (NFPA) - Developed by the NFPA, the NEC was established to address electrical safety in the workplace. While the code is updated every three years, not all states and municipalities have adopted the same version of the NEC.

NEC Article 285–Includesrequirements for connecting all SPDs rated 1000V or less to the electrical distribution system of a facility. The standard addresses surge protection to help electricians properly install hardwired SPDs.

National Fire Protection Association (NFPA)—780 Lightning Protection Code

NFPA 780 addresses the protection requirements for ordinary structures, miscellaneous structures, special occupancies, industrial operating environments, etc. It requires that devices suitable for protecting the structure be installed on electric and telephone service entrances, and on radio and television antenna lead-ins.

IEC 61643-12 Ed. 2.0 b:2008 Low-voltage surge protective devices - Part 12: Surge protective devices connected to low-voltage power distribution systems – Selection and Application principles

IEC 61643-22 Ed. 1.0 b:2011, Low-voltage surge protective devices - Part 22: Surge protective devices connected to telecommunications and signaling networks - Selection and application principles

ATIS 0600338 – Electric Coordination of Primary and Secondary Surge Protection for Use in Telecommunications Circuits.

CEA/CEDIA-CEB29: Recommended Practice for the Installation of Smart Grid Devices[JLK4].

[ARM1]This should be in the body of the paper, not in the summary

[JLK2]I am not aware that there are surage protective EMC requirements. If so list the standards that have been adopted nationally and internationally. Determine if they are guides or recommendation that have by adopted by regulators.

[JLK3]This is obsole technology and is rarely used today.

[JLK4]Note to authors, see for a discussion on EMC and Smart Grid. This reference should be reviewed to see if there is some material that should be put in the body of this white paper