Ch. 2 Article 690 Part II Requirements
690.7(B)(3)
# for bipolar source and output circuits
690.8(A)
# for calculation of maximum circuit current
690.7(A)(3)
# for the engineering supervision method for calculating maximum voltage for PV systems over 100kW generating capacity (ac system size). New in 20017. Requires a licensed professional electrical engineer to stamp the system design.
series connection and cold temperatures
What are the two factors that increase PV source and output circuit voltage
maximum rated output for dc-to-dc converter
What is the maximum voltage output for a single dc-to-dc converter output
B
When comparing between the 2014 NEC and the 2017 NEC, which of the following is not a true statement regarding the rapid shutdown requirements: a. Controlled DC conductors located outside the array boundary shall be limited to not more than 30 volts within 30 seconds of rapid shutdown initiation for the 2017 NEC versus not more than 30 volts and 240 volt-amperes within 10 sedonds of rapid shutdown initiation for the 2014 NEC. b. Controlled conductors located inside the array boundary shall be limited to not more than 80 volts within 30 seconds of rapid shutdown initiation of the 2017 NEC versus 80 volts in 80 seconds in the 2014 NEC.
larger
When sizing circuit conductors, they shall be sized to carry not less then the _______________ of 690.8(B)(1) OR (B)(2).
Module Data Sheet
Where are the Voc and temperature coefficient of Voc commonly found
ASHRAE Handbook
Where is a good place to find cold temperatures according to the NEC?
690.7(B)
section # for dc-to-dc converter source and output circuits
690.89(A)(6)
series # dc-to-dc-converter output circuit current
690.8(A)(3)
series # for inverter output circuit current
Required Ampacity for continuous current
690.8(A) current x 1.25 = 690.8(B)(1)
690.8(B)(3)
Adjustable electronic overcurrent protective device
Yes
Are wire sizes for stand-alone inverters based on continuous currents?
Output Circuit
As dc-to-dc converter source circuits are connected together in parallel to make a dc-to-dc converter output circuit, the sum of all the currents being combined shall be the dc-to-dc converter ____________ ___________ current.
690.8(B)
Conductor Ampacity
Ampacity
Current carry ability
False - does allow
Dc-to-dc converters have the ability to electronically control current and voltage which does not allow them to limit current and use smaller wires.
No
Do we base wire sizes on the stand-alone inverter's greater surge currents?
Isc x 1.25
Formula for finding maximum circuit current for "Wild" PV circuits
Inverter voltage/Max Voltage of Module; then round down
How do you find the max voltage allowed on a string for a given inverter?
# Panels x Max Voltage
How do you find the max voltage of a string?
multiple
If a PV power source has ____________ output circuits with ___________________ output voltages and has a common return conductor, the ampacity of the common return conductor shall not be less than the sum of the ampere ratings of the overcurrent devices of the individual output circuits.
continuous, NOT
If an assembly and and its overcurrent protection device is rated for __________ use at 100% of its rating, then it does __________ need to be at least 125% of its rating. Rare and used in larger currents.
power/voltage
If inverter does not have current marked how can you calculate it? (Not always the exact same as datasheet due to changes in power factor)
True
If terminals and wire are rated for 90° then you should rate ampacity in the 90° column. But if one or the other is less then you should rate ampacity in the lower column of the 310.15(B) tables
not
If the current rating of the interactive inverter side of the transformer is at least the current rating of the inverter, then overcurrent on the inverter side of the transformer is ____________ required. This is because of current-limited characteristics of the inverter not being able to hurt the transformer or overcurrent the conductors between the inverter or transformer.
60° Column
If there are not temperature ratings on terminals which column should you use on tables 310.15(B) according to NEC (probably only on test)?
power transformers
In _____________ ______________ with sources on both sides shall consider one side of the transformer, then the other as primary. Overcurrent protection shall be done in accordance with 450.3 which have different values and are often more than 125%.
Maximun Voltage
In order to calculate module _____________________ you need three things: 1. VOC 2. Temperature coefficient of VOC 3. Low Temperature
continuous
Inverter maximum current shall be the inverter __________________ current output rating
False - calculated max voltage for strings
Max voltage of an inverter is system voltage on label on the dc disconnect.
True
Maximum circuit current for one module or a number in series is the same.
continuous output
Maximum current on dc-to-dc convert source circuit shall be the ___________ ____________ current rating.
Voc (1 + Temp Coef (°C - 25°C))
Module max voltage formula
True
NEC tables 310.15(B)(16) AND 310.15(B)(17) are used to determine wire size by ampacity and temperature ratings of equipment
bipolar systems
On ________________________ if there is a ground-fault or arc-fault, the inverter is required to isolate both circuits from each other and from ground.
Calculations
One method for determining PV source circuit (string) voltage calculations. 690.7(A)(1)_________
Table 690.7(a)
One method for determining PV source circuit (string) voltage calculations. 690.7(A)(2)_________
Engineering supervision
One method for determining PV source circuit (string) voltage calculations. 690.7(A)(3)_________
NOT
Overcurrent protection devices are __________ required for circuits with sufficient ampacity for highest available currents.
at least
Overcurrent protection devices must be _ _________ 125% of the current definced in 690.8(A) Maimum Circuit Current
listed
Overcurrent protection devices used in PV dc circuits shall be _______________ for use in PV systems
True
PV circuits have two different types of currents. 1. increases by brightness of light 2.limited by smart electronics
continuous
PV system currents shall be considered to be ______________. They can last more than three hours because sun is up for more than 3 hours a day.
80V
PV systems of ___________ or greater shall be protected by a listed arc-fault circuit interrupter.
a
Per the 2017 NCE, all of the following is permitted or required for ungrounded PV systems except ________________. a. All PV source and output circuits shall have overcurrent protection. b. All PV source and output circuit conductors shall have disconnects. c. Single-conductor cable Type USE-2 and single conductor cable listed and identified as photovoltaic (PV) wire shall be permitted in exposed outdoor locations in PV source circuits within the PV array. d. All overcurrent devices shall be placed in the same polarity for all circuits within a PV system.
C
Per the 2017 NEC, which calculating maximum photovoltaic system voltage? a. When open-circuit voltage temperature coefficients are supplied in the instructions for listed PV modules, they shall be used to calculate the maximum PV system voltage as required by 110.3(B) instead of using Table 690.7. b. PV system dc circuits on or in one and two family dwellings shall be permitted to have a maximum voltage of 1000 volts or less. c. For PV systems with a generating capacity of 100 kW or greater, a documented and stamped PV system design, using an industry standard method and provided by a licensed professional electrical engineer, shall be permitted. d. For 2-wire circuits connected to bipolar systems, the maximum system voltage shall be the highest voltage between the conductors of the 2-wire circuit if on conductor of each circuit of a bipolar sub array is solidly grounded.
690.7(B)(2)
Section # for two or more series connected dc-to-dc converters
6901.10
Series # : Stand-Alone Systems
690.8(A)(5)
Series # dc-to-dc converter source circuit current
690.8(A)(4)
Series # for stand-alone inverter input circuit current
690.9(B)(2)
Series #: 100% of its rating
same
Series #: When single overcurrent protection devices are used, they should all be in the _____________ polarity.
690.11
Series #: arc-fault circuit protection (direct current)
690.9(A)
Series #: exceptions: overcurrent protection not required
690.9(B)(1)
Series #: not less than 125% of maximum currents
690.9(B)
Series #: overcurrent device ratings
690.8 (D)
Series #: sizing of module interconnection conductors
690.9(A)
Series:#: circuits and equipment
lower voltages
Stand-alone inverters require more input current at ____________________ to make the same amount of power.
690.72(A)(2)
Table # of table method of calculating Max Voltage.
dc-to-dc converters
These are characteristics of __________________________. 1. Maximum voltage is determined in accordance with instructions of ________________. 2. if instructions not included, sum up the voltage of the __________________________. conncected in series. 3. can electronically limit voltage 4. have ability to bypass the converter internally and send PV voltage through the converter.
Isc x 1.25
This is what should be used on the dc disconnect label.
True
TorF: PV output circuits have the same voltage as the PV source circuits that are combined to make the PV output circuit.
Two methods for defining PV source circuits
What are the following two items? 1.690.8(A)(1)(1) - 125% of short-circuit current 2. 690.8(A)(1)(2) Engineering supervision method for calculating maximum circuit current for PV systems over 100kW
Circuit currents in order of increasing current
What are the following: 1. Imp = current at maximum power 2. Isc = short-circuit current 3. Isc x 1.25 = maximum circuit current from applying 690.8(A)(1) 4. Isc x 1.56 = Required ampacity for continuous current from 690.8(B)(1)
single overcurrent device
Where a ___________ ______________ ____________ is used to protect a set of two or more parallel-connected module circuits, the ampacity of each of the module interconnection conductors shall not be less than the sum of the rating of the single overcurrent device plus 125% of the short circuit current from the OTHER parallel-connected modules.
on label, datasheet or installation instructions
Where is the maximum voltage located for the dc-to-dc converter?
Adjusted Voc x Modules in series
With the table method how do you find maximum system voltage after you have found the adjusted Voc?
Voc x Table correction factor
With the table method how do you get the adjusted Voc to compensate for temperature?
Bipolar system
________ has a positive grounded array section (subarray) and a negative grounded array section (subarray). Maximum voltage is considered voltage to ground.
Wiring
____________ of stand-alone systems shall be done in accordance with 710.15
Adjustable trip
_____________ ______________ breakers without restricted access shall be considered the highest trip rating possible.
Exceptions
_____________ for arc-fault protection are PV systems that are not on or in buildings, PV output circuits and dc-to-dc converter output circuits that are direct buried, in metallic raceways or in enclosed metallic cable trays. Only applies to PV and dc-to-dc converter output circuits, not source circuits.
Restricted
_______________ access adjustable-trip circuit breakers shall be permitted to hve the ampere rating equal to the adjusted trip settings
Maximum current
_______________ on stand-alone inverters shall be the continuous inverter input current when inverter is producing rated power at lowest input voltage.
Stand-alone inverters
________________ often have values for continuous current, which match the power rating of the inverter, but also have current values for surges of current that are greater than the continuous current rating of the inverter.
B.
per the 2017 NEC, one method for calculating conductor ampacities for PV system currents (name "After Application of Adjustment and Correction Factors") uses all of the following factors except for ________________________. a. The maximum currents calculate in 690.8(A). b. Ambient temperature adjustment for raceways or cables exposed to sunlight 3.5 inches above rooftops. c. Adjustment factors for more than three current-carrying conductors in conduit. d. Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).
690.8(C)
series # systems with multiple direct-current voltages
690.9
series #: Overcurrent Protection
