Forums » Electrical Engineering

PV systems

    • 5 posts
    February 6, 2019 4:01 AM PST

    Hello everyone I am in this community,

    I have a question, PV systems installed on agricultural buildings, and the sockets and circuits that can be operated for this building and outside building must be GFCI or protected by RCD protectors?

    Rgs

  • February 6, 2019 4:20 AM PST
    As far as I know RCD and GFCI are the same equipment.
    A circuit breaker or a switch disconnector sensitive to earth fault current.
    And yes, you must use this type of protectors.
    • 141 posts
    February 6, 2019 4:57 AM PST

    I am not sure of the rules for Ag buildings in Europe, Asia, etc but the NEC is clear and the NEC only recognizes GFCI.  I believe Manuel is correct that the RCD is the overseas counterpart to our GFCI.  Not sure if the trip rate is the same-- GFCI starts about 4-6 ma.

     

     

    547.5(G) Receptacles. All 125-volt, single-phase, 15- and 20-ampere
    receptacles installed in the locations listed in (1) through (4)
    shall have ground-fault circuit-interrupter protection:
    (1) Areas having an equipotential plane
    (2) Outdoors
    (3) Damp or wet locations
    (4) Dirt confinement areas for livestock


    This post was edited by Dennis Alwon at February 6, 2019 4:57 AM PST
    • 5 posts
    February 6, 2019 5:44 AM PST

    Thank you. 

    Does anyone know about lightning protection in PV systems?

    • 62 posts
    February 6, 2019 5:59 AM PST

    It should be done with care, in case of failure of vertical air terminals, the cost of damage can be too high

    • 200 posts
    February 6, 2019 6:03 AM PST
    Thanks for the suggestion of this topic.

    For the sake of knowledge of all Z4E Members:

    PV System: Photovoltaic system or solar power system, designed to supply usable solar power by means of photovoltaics. It includes solar panels to absorb and convert sunlight into electricity, an inverter to change the electric current from DC to AC, and other electrical accessories;

    GFCI: term normally used in the USA. The standard trip setting is about 5mA which gives good protection against electric shock, they are Ground-Fault breakers for personnel safety with "Class A" Protection, with trip value set at 5mA +/- 1 mA. They can fit in a panel, or built in to a receptacle/socket outlet, also protect any downsteam outlets on the same circuit. A GFCI breaker typically is part of a load center or panelboard system.

    RCD: Residual Current Device, term normally used in the UK, and the most common trip rating is 30mA though many other ratings exist, there are RCD breakers from <10mA to 300mA trip. They are usually a separate panel mount device (such as a DIN rail mounted mini circuit breaker) and is designed specifically for Equipment Protection, similar to the US Ground-Fault breakers GFEP. UK RCDs normally only protect against leakage to earth/ground, and do NOT protect against overload or short circuit, a fuse or MCB must also be employed to protect against such events. A combined earth leakage and overload protective device is available, these are known as RCBOs in UK. UK RCDs built into an outlet do NOT protect downstream outlets. The common 30mA trip current does NOT provide total protection for personnel against shocks, but UK RCDs have faster acting than US GFCIs.

    I hope this helps.
    This post was edited by Alex de Moura at February 6, 2019 6:29 AM PST
    • 7 posts
    February 6, 2019 6:47 AM PST
    I have a problem with PV. This is tangent to the GFI discussion but needs to be mentioned. If you observe disaster conditions such as fire. The equipment hazards exist such that individual panels are not always circuit breaker protected and in the case they are, still doesn’t trip during a fire where water is supplied to extinguish the fire. Therefore a hazard exists as long as sunlight is available the panels themselves produce electricity. GFI MAY shut outlets off but not the panels. This puts emergency personnel at risk to control accidents and with panels producing energy, it makes it worse. Therefore when designing for failsafe conditions include shorting bar or black out cover device to dead metal your power source! I have not seen yet a safety device or procedure to satisfy my acceptance of solar panels.
    This post was edited by Paul Travers at February 6, 2019 6:50 AM PST
    • 62 posts
    February 6, 2019 7:35 AM PST

    This can be one solution to isolate the grid before taking fire

     

    • 200 posts
    February 7, 2019 8:00 AM PST
    Paul Travers said:
    problem with PV... disaster conditions such as fire... hazards exist such that individual panels are not always circuit breaker protected and in the case they are, still doesn’t trip during a fire where water is supplied to extinguish the fire... panels themselves produce electricity... and with panels producing energy... designing for failsafe conditions include shorting bar or black out cover device to dead metal your power source... not seen yet a safety device or procedure to satisfy my acceptance of solar panels.

    Sincerely, this one is very good, the main reason why Members came to Z4E (and to old Z4I).

    I suppose at this time some Code or some Standard Commitee had already addressed this issue. Personally, power system+protection system experience doesn't include solar power systems (too much theory, no Practice).

    Now we can imagine an entire power grid for public service, not a building or a farm, there is a lot of power (DC voltage) on cabling mesh connected to every single panel to the next main breaker.

    In a hazardous event, even if the Main breaker trips there is no reason for each individual panel breaker to trip, the current is zero, fresh outdoor temperature, even more with fire system water sprinkling on them... and the power still there on grid cabling mesh... scorch the sky to block the sun as in "Matrix" is not possible.

    I didn't check the SOL30 device advised by Reynaldo yet. It shall be installed on every single panel, or small set of them?

    Anyone? An standard, or code or a practical solution perhaps?

    (Sorry, very hard too edit in Android, when quote)
    This post was edited by Alex de Moura at February 7, 2019 8:10 AM PST
    • 62 posts
    February 7, 2019 10:14 AM PST

    This switch disconnects the photovoltaic systems or a module from the rest of system as quick as possible.
     This DC load break switch (32A) is mounted in the PV Modules. It is installed in the position where the current is passing from the PV modules to the inverter. This switch can also be operated from a remote location by means of a PV emergency stop button. It is commonly installed in EU PV Grid but do not know its usage worldwide.

     

  • February 7, 2019 3:19 PM PST

    Disclaimer:  I am just getting started with PV.  Well, except for the 200W, 24V system I put in at a remote access cabin to keep the batteries charged, 20years ago.  There is a lot I don't know.

    NEC 2014 and 2017 have introduced Art. 690.12, Rapid Shutdown of PV Systems on Buildings.  I have not seen one.

    The sol30 Reynaldo describes fits the 690.12 definition.  It open circuits the PV sources close to the source using a remote switch.

    • 200 posts
    February 7, 2019 5:28 PM PST
    The SOL30-SAFETY works by disconnecting the PV panels from the rest of the system as soon as the main AC breaker is tripped or switched by the firefighters. This is achieved by the inherent under voltage release which automatically disengages the SOL30-SAFETY when the AC voltage is not present. The fireman’s safety switch is rated at 1000V DC, 30A and can be manually switched as well. And the catalogue says it can be installed outdoors, so as near as possible of grid. It trips voltage monitoring AC voltage, meaning it responds to hazardous events that trip the inverter.
    • 7 posts
    February 7, 2019 10:09 PM PST
    PV installations should be installed in accordance with national guidance (MCS, 2012) and any specific guidance issued by manufacturers. There are a number of standards that PV products should comply with (BS EN 61730-1, BS EN 61215, BS EN 61646, MCS 0065) which include (amongst other factors) requirements that address fire hazards.
    • 7 posts
    February 7, 2019 10:34 PM PST
    Carl Coulter said:

    Disclaimer:  I am just getting started with PV.  Well, except for the 200W, 24V system I put in at a remote access cabin to keep the batteries charged, 20years ago.  There is a lot I don't know.

    NEC 2014 and 2017 have introduced Art. 690.12, Rapid Shutdown of PV Systems on Buildings.  I have not seen one.

    The sol30 Reynaldo describes fits the 690.12 definition.  It open circuits the PV sources close to the source using a remote switch.


    The following steps should be followed to protect PV system, but nothing in NEC book for PV protection Disconnect load switch on the DC side at or in the inverter . Isolation load switch at the transition to the module field. short-circuit protector in each individual PV module
    This post was edited by Rechart Grand at February 7, 2019 10:37 PM PST
    • 7 posts
    February 8, 2019 6:05 AM PST
    I have read comments from you on safety devices to shut panels down. Again the response are, the devices are not well known, or the emergency device placed close as possible to the panel, and there is a remote shut off. Let me explain something to you. Place yourself in a building with people screaming and a fire is in process. There is no maps, no lights, NO standard hardware located at the front door saying HIT ME!
    Replace the solar panels with 100 Hp driven gas generators mounted through out a building. As a Fire Fighter making his or her way to saving people extinguishing fire and spraying water on electrical equipment. What hazards are present? What procedures need be given to solar panel manufacturers to unify the proper shut down of the Panel? Such that it has universal acceptance such as HIT THIS BUTTON, just like a fire alarm. I don’t want to add a private build emergency switch and explain how it works. I need universal knowledge for everyone to know the shut off valve and where to find it. Then solar panels mounted on wooden homes or factory buildings are safe. My point- its a good invention just implemented hazardously.
    • 129 posts
    February 8, 2019 8:55 AM PST
    Rechart Grand said:
    Carl Coulter said:

    Disclaimer:  I am just getting started with PV.  Well, except for the 200W, 24V system I put in at a remote access cabin to keep the batteries charged, 20years ago.  There is a lot I don't know.

    NEC 2014 and 2017 have introduced Art. 690.12, Rapid Shutdown of PV Systems on Buildings.  I have not seen one.

    The sol30 Reynaldo describes fits the 690.12 definition.  It open circuits the PV sources close to the source using a remote switch.


    The following steps should be followed to protect PV system, but nothing in NEC book for PV protection Disconnect load switch on the DC side at or in the inverter . Isolation load switch at the transition to the module field. short-circuit protector in each individual PV module

     

    it is already mentioned by Carl the reference. The Section 690.12 of  2017 National Electrical Code (NEC) is  for PV system. 

    • 62 posts
    February 10, 2019 12:18 PM PST
    Mike Robert said:

    Thank you. 

    Does anyone know about lightning protection in PV systems?

    Another photo regarding lightning protection

     

    • 5 posts
    February 10, 2019 12:25 PM PST

    Thank you. The safety standards applied are IEC 61730 in Europe / Asia