1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES INC. CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared and published by Underwriters Laboratories Inc.(UL). It is normative for the a
2、pplicable UL Product Certification Program(s); however, it is currently notpart of the UL Standard(s) referenced below.Product Category (CCN): QIKHStandard Number: UL 1741Edition Date: January 28, 2010Edition Number: 2Section / Paragraph Reference: New proposed sections 87 to 100.Subject: Non-Isolat
3、ed EPS Interactive PV Inverters Rated Less Than 30KvaDECISION:The requirements below, (include new definitions and Sections 88 100) are to be used for the evaluationof transformerless / non-Isolated EPS interactive PV inverters with PV array inputs and correspond article690.35 of the NEC.General The
4、se requirements address Non-Isolated EPS Interactive PV Inverters with PV array inputsinstalled in compliance with NEC 690.35 and do not contain a PV array circuit grounding connectionwithout a limiting impedance as defined by these requirements.DefinitionsCritical Isolation Component - A component(
5、s) such as a contactor or relay that isolates the PV arrayinput connection and associated circuitry from the EPS connections and associated circuitry.Isolation Monitor Interrupter (IMI) - A device that monitors the insulation resistance of a PV array circuitto ground and prevents energization of the
6、 inverter AC output circuit or disconnects an energized outputcircuit when the PV array input circuit insulation resistance drops below a predetermined value. Some IMIsmay have monitoring circuitry that verify functionality and take appropriate actions in the event of circuitfailures. The IMI circui
7、t may include or provide signals to control the critical isolation components.Ground Fault - An unintentional current path from ground to a component or circuit.Inverter Backfeed Current Inverter current flow to the PV array and its wiring under inverter normal orsingle fault abnormal conditions.Non
8、-Isolated Inverter - An inverter that does not provide galvanic isolation between its input and outputcircuits.Functional Ground - An intentional impedance path from ground to a component or circuit in a PV arrayand/or inverter circuit. Functional grounding may be used during PV array isolation meas
9、urements. Theintentional impedance path to ground may be a permanent or temporary connection. A permanent PVarray connection to ground without limiting impedance is not considered a functional groundNon-Isolated Inverters for use in Photovoltaic Power Systems87 GeneralUL COPYRIGHTED MATERIAL NOT AUT
10、HORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULThese requirements cover permanently connected, non-isolated PV Utility Interactive inverters that areinstalled on ground referenced EPS source circuits.87.1 The requirements in sections 87 100 are in addition to the other req
11、uirements in UL 1741.Exception: The GFDI requirements in Section 31 do not apply to non-isolated inverters.Construction88 General88.1 Non-isolated inverters specific construction and operational requirements are covered in sections 89through 92.88.2 When an isolation monitor interrupter relies upon
12、software or firmware to comply with therequirements in sections 89-92, the software of firmware shall be evaluated for reliability in accordancewith the Standard for Software in Programmable Components, UL 1998.88.3 An isolation monitor that has an adjustable trip setting shall also have a means to
13、prevent tamperingwith the setting or shall be otherwise protected from general user access.88.4 An isolation monitor interrupter shall have a built-in self- test circuit or means to automaticallyconnect circuitry to verify correct operation of the isolation monitor interrupter. The automatic self-te
14、stfeature shall verify the isolation monitor interrupter is functioning within its intended operating limits. If theisolation monitor interrupter self test circuit determines it is outside its intended operating limits, the unitshall prevent the closing function of the critical isolating component t
15、hat separates the PV arrayconnection and associated circuitry from the EPS connections and associated circuitry and indicate thefault.88.5 The self- test mentioned in 88.4 shall be performed prior to connection and export of energy to theEPS and at least once in each 24-hour period.88.6 Loss of powe
16、r to the Isolation monitor interrupter shall result in the opening of the critical isolatingcomponent to separate the PV array connection and associated circuitry from the EPS connections andassociated circuitry.88.7 Components in an isolation monitor interrupter circuit shall be analyzed to determi
17、ne the potential forthe malfunction that could result in misoperation, the disabling of, or have a negative impact on theintended operation of the IMI monitoring system including control circuits, measuring circuits, or the powersupply to such circuits (e.g. capacitors, diodes, solid-state devices,
18、current transformers, voltagemeasurement resistors, and similar components. Faults are to be short or open circuited any twoterminals, one pair at a time. Critical components shall be identified by the failure mode and effect analysisin accordance with the Standard for Tests for Safety-Related Contr
19、ols Employing Solid-State Devices, UL991.88.8 If the component analysis required in 88.7 shows that the malfunction of one or more componentsmay render the isolation monitor interrupter inoperative, the components shall comply with section 88.9.88.9 With reference to 88.8, the circuits and the ident
20、ified components are to be subjected to the followingtests (to be run on IMI circuitry as a preconditioning to the functionality tests), in accordance with themethods described in Section 99 - Tests for Safety-Related Controls:a) Surge withstand performance test as outlined in section 99.1.STANDARD
21、NUMBER: UL 1741 -2-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULb) Protection from electromagnetic interference as outlined in section 99.1.c) Ramp Voltage Test (Verified operation at extremes of PV and Utility ranges of operatingvoltages)
22、as outlined in section 99.2.d) Electrostatic Discharge Test as outlined in section 99.3.e) Thermal Cycling Tests, Test performed at 20C to +85C or manufacturer specified storagetemperature range, whichever is most severe) as outlined in section 99.4.f) Humidity cycling Test as outlined in section 99
23、.5.Exception: Alternatively, circuits and components may comply with the equivalent requirements from theStandard for Test for Safety-Related Controls Employing Solid-State Devices, UL 991.88.10 An isolation monitor interrupter that has tripped on the Continuous fault current limit as defined intabl
24、e 89.1 is not permitted to be capable of automatic reclosure.Exception: An isolation monitor interrupter may automatically reconnect, provided it is limited to no morethan 4 reconnections within a 24 hour period.Note: The allowance for the IMI to automatically reconnect (after measuring the array im
25、pedance) isbased upon the likelihood that the sudden change leakage current thresholds as defined in table 89.2 willbe exceeded under some normal operating conditions. For example, rain showers covering large portionsof a PV array can result in a step change in leakage current that are not always in
26、dicative of an actualisolation failure.89 PV Array Isolation Monitor Interrupter89.1 A isolation monitor interrupter may be used with ungrounded arrays or functionally grounded arraysto limit ground fault and backfeed current to the array and the protective earth connection. This deviceshall limit t
27、he current of isolation fault hazards by restricting the ability of the unit to connect to the gridwith ungrounded and functionally grounded arrays when the system exceeds the limits defined in 89.2below. Additionally, the PV array isolation monitor interrupter shall monitor for sudden changes in th
28、eisolation fault current as outlined in 89.4 below:89.2 The PV array isolation monitor interrupter shall continuously monitor for isolation fault current asspecified in Table 89.1 listed below. When the continuous fault current exceeds the limits in table 89.1 theunit shall open the critical isolati
29、on components to disconnect the inverter AC output connection within thespecified time limits.STANDARD NUMBER: UL 1741 -3-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULTable 89.1Inverter Power Rating Maximum Continuous Fault CurrentLimitMaxi
30、mum Allowable Time to openthe critical isolation component.(Seconds) 30 kVA 300 mAa0.3a - A manufacturer may specify up to a +5% measurement tolerance on this limit.89.3 The PV array isolation monitor interrupter shall comply with the Continuous Isolation MonitorInterrupter Fault Current Limit Test
31、outlined in section 94.89.4 The inverter shall open the critical isolation components within the parameters specified in Table89.2.Table 89.2Maximum Sudden Increase in Isolation Fault CurrentMagnitudeMaximum Allowable Time to open the critical isolationcomponent. (Seconds)30 mA 0.360 mA 0.15150 mA 0
32、.0489.5 The PV array isolation monitor interrupter shall comply with the Sudden Change Isolation MonitorInterrupter Fault Current Test outlined in section 95.89.6 A PV array isolation monitor interrupter shall be able to function as required by section 89.1 in thepresence of single component fault c
33、onditions. Single component faults, critical to the operation of thesystem, shall be evaluated within a PV array isolation monitor interrupter, associated control circuits, orpower supply to applicable system circuits. To evaluate the systems operation under abnormal single faultconditions, the syst
34、em shall comply with the Isolation Monitor Interrupter Component Short / Open CircuitTest specified in section 96 and indicate the occurrence of the system fault.Exception No. 1: A PV array isolation monitor interrupter disabled by a single fault such that it is unableto comply with section 89.1, is
35、 permissible, provided the following conditions are met:a) The system detects the fault,b) The system indicates that a fault occurred,c) The inverter opens the critical isolation components to disconnect the inverter AC outputconnection from the EPS,d) The inverter shall keep open the critical isola
36、tion components under any sequence ofremoving and/or reconnecting input power, output power, or both, ande) There is no user-reset option to clear a component fault.Exception No. 2: A PV array isolation monitor interrupter disabled by a single fault such that it is unableto comply with section 89.1,
37、 is considered to comply with the above requirement provided the followingconditions are met:a) The system detects the fault,STANDARD NUMBER: UL 1741 -4-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULb) Indicates that a fault has occurred,c)
38、Continues to operate in accordance with section 89.7,d) Once the inverter has opened the critical isolation components to disconnect the inverter ACoutput connection as outlined in section 89.7, it shall remain open under any sequence ofremoving and/or reconnecting input power, output power, or both
39、 until the fault has beenrepaired and the system has been reset, ande) There is no user-reset option to clear a component fault.89.7 A component fault that impairs the IMIs ability to function as required by Section 89 shall not resultin continued operation of the inverter .after the input source is
40、 removed or reduced below the minimumoperating level of the inverter, but for no more than 24 hours while in the impaired state.90 Insulation Resistance Detection of Ungrounded PV Arrays90.1 Inverters connected to ungrounded PV arrays shall have an insulation resistance detection means tomeasure the
41、 DC insulation resistance between the PV array input(s) and earth ground. The unit shall:a) measure the insulation resistance between the PV array input circuit(s) to ground prior toclosing the critical isolation components to export of power to the EPS, andb) be able to detect insulation resistance
42、 values below the limits stated in table 90.1.Table 90.1Inverter Maximum Power Rating Minimum DC insulation resistance allowed between thePV array input(s) with respect to ground 5 kVA The larger resistance of 100kor(1 k *Vmax)5 kVA The larger resistance of 100kor(5000 * Vmax) / (Smax)Vmax = manufac
43、turer rated maximum PV input voltageSmax = maximum rated inverter output apparent power in kVA90.2 The product shall comply with the Array Insulation Resistance Measurement Test as outlined insection 97.90.3 The product is to indicate a fault and prohibit closing the critical isolation components to
44、 connect tothe EPS when the DC insulation resistance measured is less than the minimum value as defined in table90.1.91 Insulation Resistance Detection of Functionally Grounded PV Arrays91.1 Inverters may be designed to temporarily or permanently connect a predetermined value ofresistance between th
45、e PV array input(s) and ground as a means to monitor or measure the level of PVarray insulation resistance.While the predetermined design resistance value is connected to ground for insulation resistancemeasurement purposes, products employing this method must comply with the following:STANDARD NUMB
46、ER: UL 1741 -5-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULa) The predetermined design resistance must be greater than or equal to the following:Predetermined Resistance = Rated Inverter Maximum PV Input Voltage/6mAException: The predeterm
47、ined design resistance value may be lower than as stated initem A, provided the inverter complies with the Section 94 Continuous IMI Fault CurrentLimit Test and the Section 95 Sudden Change IMI Fault Current Test with the insulationresistance detection circuit connected and operating.b) The inverter
48、 shall measure the DC insulation resistance between the PV input(s) and groundprior to closing the critical isolation components to determine if the parallel combination of(measured PV array resistance and predetermined design resistance) is greater than or equalto 80% of the minimum predetermined d
49、esign resistance of the inverter as calculated in 91.1(a).c) If the measured DC insulation resistance is not greater than or equal to the 80%requirement, the inverter shall indicate a fault and prohibit connection to the EPS.d) The inverter is to comply with the test in paragraph 97.2, Array Insulation ResistanceMeasurement Test for Functionally Grounded PV Arrays. The Array Insulation ResistanceMeasurement test shall be conducted using a value of total resistance (actual design resistancein parallel combination with the test resistance) which is less than or equal to 8
