1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES INC. CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared by UL LLC. It is normative for the applicable ULProduct Certification Program(
2、s); however, it is currently not part of the UL Standard(s) referencedbelow.Product Category (CCN): QIKHStandard Number: UL 1741Standard Title: Standard for Inverters, Converters, Controllers and InterconnectionSystem Equipment for Use With Distributed Energy ResourcesEdition Date: January 28, 2010E
3、dition Number: 2Section / Paragraph Reference: New Sections 2.1.7A, 2.1.28A, 2.1,30A, 2.1.31A,2.1.39A, 2.1.40A, sections (14.1.4- 14.1.5.6), 14.3, 14.3.1, 19.2.1 to 19.2.3, 19.3Exceptions 1) and 2), 19.5, 47.1.8, new sections (46.2, 46.3 and 46.4), 47.1.8, 64.16and 64.17. Revisions 2.1.42, 19.1, 19.
4、2, 19.3 and 63.15.Subject: Clarification of Multi-Mode Inverter Requirements Including SupplyConductor GroundingDECISION:Definitions2.1.7A CLOSED TRANSITION TRANSFER A switching event with overlapping connections betweentwo AC power sources (to provide a make before break transfer operation) that ar
5、e synchronized at thetime of transfer. The two sources shall be paralleled for no more than 100 ms.2.1.28A MAIN BONDING JUMPER The conductor used for the connection between the groundedservice conductor (typically the neutral conductor) and the equipment grounding conductor.2.1.30A MULTI-MODE INVERT
6、ER An inverter with both utility interactive capabilities and standaloneinverter capabilities. Some multimode inverters are capable of switching between operational modesautomatically depending on utility availability or other pre-defined conditions. Some products can performan open transition trans
7、fer, some can provide a closed transition transfer between modes and some canperform both depending on settings.2.1.31A OPEN TRANSITION TRANSFER A switching event that provides a break before make transferoperation between two power sources such that the load is intentionally disconnected from both
8、sources.2.1.39A SEPARATELY DERIVED SOURCE An Electrical Power Source, (other than an electric utility),having no direct connection(s) to any other electrical source except for grounding and bondingconnections (from NFPA 70).2.1.40A SERVICE EQUIPMENT Equipment that serve to connect to the service con
9、ductors load end toa building, structure, or otherwise designated area, and is intended to provide the function of main controland supply disconnect. Service equipment typically includes Over current protection (circuit breaker(s) orfuse(s), switches and applicable accessories. Utility interactive,
10、standalone and multimode products mayperform service equipment functionality including the service neutral to ground bond (From NFPA 70)2.1.42 STAND-ALONE INVERTER An inverter intended to supply a load and does not provide powerback to the electric utility. Some stand-alone inverters have an EPS or
11、other AC input sourceconnection(s) that can supply power to loads and or charge energy storage systems.UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULAdd the following Sections to UL1741.14.1.4 Stand-alone inverters that receive EPS or other
12、AC input source power to supply loads shallcomply with the Backfeed Test in Sections 14.1.5 and 46.4 to all sources of input AC power.14.1.5 Backfeed Protection14.1.5.1 A standalone inverter that has an EPS or AC input source connection UPS shall be provided withbackfeed protection to prevent a pote
13、ntial involving a risk of electric shock (see Electric Shock, Section11) from being present on its input ac terminals and or backfeeding the EPS or AC input source circuitduring inverter power generation.14.1.5.2 With reference to the requirement in 14.1.5.1, performance of the protection is to be j
14、udged byconducting the Backfeed Protection Test, Section 46.4.14.1.5.3 The protection mentioned in 14.1.5.1 shall employ an automatic switching device having air-gapcontacts such as an electromechanical relay for preventing a potential involving a risk of electric shockfrom appearing on the AC EPS o
15、r other AC input terminals.Exception: An electronic control employing a solid state power switching component and subjected to thetests described in 14.1.5.4 may be provided in lieu of an air-gap contact device.14.1.5.4 The backfeed protection for stand-alone inverter, with an output that is not a s
16、eparately derivedsystem, shall open or de-energize all supply conductors when subjected to the requirements specified fora GFDI circuit in paragraphs 31.5 31.10 except the functionality being evaluated is backfeed protection.14.1.5.5 With reference to 14.1.5.4, the conditions described in either (a)
17、 or (b) resulting from ashort-circuit failure of a solid-state component during the normal mode of operation that is used forisolation between the input-ac terminals and the inverter is considered to comply with the requirement in14.1.5.4.a) Operation of an input-ac, overcurrent-protective device; o
18、rb) Shut-down of the inverter.14.3 Multi-Mode Products14.3.1 Multi-Mode products shall comply with multi-mode requirements, requirements for stand-aloneproducts, charge controllers if applicable, and the requirements for utility interactive products.19.1 The requirements for circuit grounding specif
19、ied in 19.3 19.5 apply to the ac output circuit of astand-alone inverter, multimode inverters and utility interactive inverters that include a means to bond theAC output circuit to ground within the product shall comply as required in 19.3.19.2 An inverter intended to be utility-interactive (not ser
20、vice equipment rated) shall not have a direct/solidelectrical connection between any output ac conductor and the enclosure. If the inverter is capable ofchanging to a standalone operating mode then 19.3 shall apply during the standalone operation if theinverter transitions the wiring system bonding
21、to a separately derived Neutral-ground bonding system.19.2.1 A Multi-Mode or standalone inverter relying on service conductor bonding by a separate piece ofequipment, that is in a nonseparately derived system, shall have the marking described in 64.17.STANDARD NUMBER: UL 1741 -2-UL COPYRIGHTED MATER
22、IAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM UL19.2.2 Multi-mode or standalone inverters that switch between multiple ground bond locations shall notallow the switching action to result in a temporal gap in system ground bonding (such that the system canbecome u
23、ngrounded) and the switching event shall not allow for an overlap with multiple ground bondsfor more than 0.1 seconds as verified though the Ground Bond Transfer Switch Timing Test 46.2.Note: this requirement is intended to prevent operation without a ground bond, or multiple bonds in the wiring sys
24、tem.19.3 Other than as specified in 19.2.1 19.2.3, each ac output circuit shall have a grounded conductor.The ac output circuit conductor to be grounded shall be as follows:a) Single-phase, 2-wire one conductor.b) Single-phase, 3-wire the neutral conductor.c) Multiphase system having one wire common
25、 to all phases the common conductor.d) Multiphase system in which one phase is used as in item (b) the neutral conductor.e) One conductor of a corner grounded delta circuit.f) The midpoint of one phase winding of a 3-phase, 4-wire, delta circuit.Exception No. 1: The following provisions are to be pr
26、ovided in order for the circuit conductor to begrounded in the field if not provided in the factory:1) A jumper is connected to ground as specified 19.4 (a or b), identified as indicated in 64.17and 65.2.9; the free end is insulated,2) A field-wiring terminal is provided to accept the jumper,3) The
27、size of the terminal and jumper shall be based on the current rating of the circuit, but notbe less than that specified bonding conductor size specified in Table 19.1 and identified inaccordance with 64.17 and 65.2.9,4) A field-wiring terminal intended for the grounding electrode conductor shall be
28、provided andsized as specified in Table 18.1 column 3 and identified in accordance with 64.16,5) A marking identifying the circuit as a separately derived source and referencing theinstruction manual in accordance with 64.17 and 65.2.9.19.5 The size of the bonding jumper specified in 19.4 shall not
29、be less than specified in Table 19.1.Exception: A smaller conductor or contacts of a relay/contactor may be used if the path complies with:a) The Bonding Impedance test section 48, andb) The Bonding Conductor test section 52.46.2 Ground Bond Switch Timing TestSTANDARD NUMBER: UL 1741 -3-UL COPYRIGHT
30、ED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM UL46.2.1 Multi-mode products that switch between multiple ground bond locations shall be tested to verifythere is no temporal gap in system ground bonding (such that the system can become ungrounded) andthe sw
31、itching event shall not overlap with multiple service conductor ground bonds for more than 0.1seconds.46.3 Synchronization Device test46.3.1 Multi-mode inverters shall comply with the Standard for Interconnecting Distributed Resources WithElectric Power Systems, IEEE 1547, Section 4.1.3 Synchronizat
32、ion, and the Standard for ConformanceTest Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, IEEE1547.1, Section 5.4 Synchronization test.46.4 Backfeed protection test46.4.1 Within 1 second of disconnect from the EPS, a standalone or a multi-mode product shal
33、l not haveHAZARDOUS VOLTAGE or energy on the EPS input or other AC source terminals. Backfeed shall beprevented from both power circuits and non-power circuits when the product is generating power from aNon-EPS source. This is verified through measurement with the EPS source disconnected.46.4.2 Whil
34、e the multimode product is generating power with the EPS disconnected, the followingconditions shall apply for both no-load and full-load conditions:a) Under normal and any single fault conditions, there shall not be an electric shock hazardwhen measured between any two AC input terminals as defined
35、 by the limits in section 11.b) Protection circuit, if provided shall operate within 15 s of the disconnection of the AC inputpower when measured at the permanent field wiring terminals and within 1 second s whenmeasured at any accessible pins on connectors that may be opened without the use of tool
36、s.46.4.3 Single fault conditions shall be determined by circuit analysis and/or investigation, and shall includepotential load faults such as phase-to-earth isolation failures.47.1.8 After each abnormal test for Multimode products, the switching devices that transfer betweensources and between groun
37、d bond shall not lose their intended functionality. Switching devices shall notfail in a short circuit condition such as a welded contact, or fail in an open circuit condition such as stuckopen. Switching devices shall not otherwise lose segregation or isolation between circuits not intended tobe co
38、nnected63.15 A terminal for the connection of a grounded conductor and the main bonding jumper shall beidentified by means of a metallic plated coating substantially white in color, and shall be readilydistinguishable from the other terminals; or identification of the terminal for the connection of
39、the groundedconductor shall be clearly shown in some other manner, such as:a) A marking on the unitb) An indication on a wiring diagram attached to the unit, orc) Information provided in the instruction manual.STANDARD NUMBER: UL 1741 -4-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTIO
40、N ORDISTRIBUTION WITHOUT PERMISSION FROM UL64.16 A unit having an output ac circuit that is intended to be grounded in the field shall be marked withthe following or equivalent words: Warning - Risk or Shock and Fire - The output ac circuit is consideredas a separately-derived source. When grounding
41、 of this output AC circuit is required, use terminal (identifyterminal) for bonding this circuit to the enclosure. Ground the enclosure to a grounding electrode inaccordance with local jurisdiction requirements.64.17 A multi-mode inverter relying on bonding originating in another wiring system when
42、in standalonemode shall have the following warning located near the neutral terminal “Warning - Risk or Shock and Fire- No internal bonding. DO NOT operate without connection to a wiring system with Neutral to groundbonding.”65.2.9 Units that have a service ground bond or are intended to be connecte
43、d to other equipment with aservice ground bond, shall have clear instructions that the end installation shall have one and only oneground bond for the system. The instructions shall clearly define how the ground bond is to be made andwhere it is to be located. The instructions shall provide referenc
44、e to the applicable portion(s) of NECArticle 250.65.2.10 Installation instructions for multimode units shall include reference(s) to the NEC 705, 706 and710 that require directory plaques for all service equipment identifying all electric power sources.RATIONALE FOR DECISION:When UL 1741 was origina
45、lly published it anticipated that inverters would either have standalone or utilityinteractive functionality. As such UL 1741 anticipated that a supply ground bond connection (main bondingjumper) would only be needed for stand-alone inverters, because utility interactive inverters would beconnected
46、to other service entrance equipment that would include the neutral to ground bond connection.The existing requirements need to be expanded for products that can operate in both standalone modeand grid interactive mode (i.e. multi-mode inverters). The above requirements will clarify the neutral togro
47、und bonding requirements for multi-mode inverters, as well as for products that connect to otherequipment that include the Neutral to Ground bond. These new requirements will also clarify otherrequirements for multi-mode inverters.Historically, utility interactive inverters have had a single output
48、circuit and bonding of the neutral wassupplied at the service equipment. Inverters are becoming more complex and include multiple outputs, forboth utility interactive and standalone functionality. Some of these inverters may be required to switch thesupply conductors from bonded to isolated during t
49、ransfer between modes. This CRD is intended to clarifythe standard with respect to the operation of multi-mode inverters.Existing utility interactive inverters are required by IEEE 1547.1 to cease current export to the EPS undergrid fault conditions and IEEE 1547.1 does not require an airgap device to open to fulfill this requirement.There are also certified semiconductor transfer switches in accordance with UL 1008S. With this in mind,the multimode products will similarly cease to export current to the EPS when not in a mode of exportingcurrent to the EPS
