Job Sheet 3 – Trainer Components - Lab-Volt · Job Sheet 3 – Trainer Components ... A...

© Festo Didactic Inc. 88191-20 13

Job Sheet 3 – Trainer Components

Grid-Tied Equipment

The electric utility grid is a large-scale power system that is maintained by electric utility

companies across the United States. Alternative energy systems that convert solar or wind

power to electricity can supply electric power to the utility grid. Figure 3-1 shows one example

of a simple solar energy system that is grid-connected, or grid-tied. It is a block diagram of a

utility-interactive system.

Figure 3-1. Typical Grid-Tied Solar Energy System.

modules provides a high DC voltage to the input of a string inverter. The addition of parallel-

connected sub-arrays offers higher current and more overall input power to the inverter. The

main function of the inverter is to convert DC voltage to an AC voltage, which is compatible with

the local utility grid. The AC output from the inverter is commonly distributed throughout the

residential house or commercial building via an AC power load center or AC power distribution

panel (also called a main service panel), which contains AC circuit breakers for each electrical

load branch. The utility grid is connected to the load center through a utility (kWh) meter, which

tracks energy usage as it is imported or exported in or out of the renewable energy system.

Inverter operation is intended to be fully automatic.

voltage and frequency are correct, the inverter starts feeding energy to the grid. At dusk, the

sunset decreases irradiance on the solar array. Once power drops to an inadequate level, the

inverter stops feeding energy to the grid.

Additional parts and equipment are typically needed to correctly install a solar power system,

such as a DC disconnect switch on the DC input to the inverter, and an AC disconnect switch

on the AC output from the inverter. Some string inverters have disconnect switches already

integrated into their enclosure. Most string inverters also include a host of other features

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14 © Festo Didactic Inc. 88191-20

and functions as well, such as a digital display, optional remote displays, data logging, data

communication ports (Ethernet, telephone, serial, etc.), external sensors (temperature,

built-in circuit protection, including string fuses. A ground-fault detection and interruption (GFDI)

circuit may be incorporated into the inverter to ensure compliance with NEC and UL standards.

There are many commercially-available brands of string inverters that include:

•

•

• Samlex America Soleil series

• SMA America Sunny Boy series

•

Additional parts and equipment that are often required for a solar power system include

mounting hardware, wire, conduit, combiner and junction boxes, DC circuit breakers, a ground-

Installation

In the United States, electrical installations must be in accordance with the National Electrical

regulations for the site as well, such as UL, CSA, IEEE, and FCC.

interact with the utility grid. This procedure assumes that the solar array is mounted on the roof

already.

• Choose an appropriate indoor or outdoor location for the power inverter.

• Mount the power inverter on the wall vertically.

• Turn off the utility grid circuit breaker before wiring.

• Cover all solar modules with opaque material or install the DC wiring at night.

•

install conduit and pull wires as needed for the system.

•

• Select and install the proper AC branch circuit breaker or fuses and AC disconnect.

• Connect the electric utility grid based on the electrical AC service provided.

• Connect a GFDI circuit for either positive or negative DC ground as required.

• Select and install the proper DC string fuses and DC disconnect.


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• Connect the solar module strings and add a combiner box, if needed.

• Close the power inverter cabinet and all box covers.

• Label all boxes as required by the NEC.

• Turn on the utility grid circuit breaker.

Figure 3-2, respectively.

Figure 3-2. Wiring of AC Power.

NOTE:

The DC inputs to the inverter can be wired from multiple strings of solar modules, as shown

in Figure 3-3. Refer to the NEC for information regarding the use of fuses and fuse holders

as DC disconnects in source circuits. External disconnect switches may be required by local

authorities known as the authority having jurisdiction (AHJ).

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Figure 3-3. Wiring of DC Strings.


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Refer to the NEC for information regarding AC disconnects.

Figure 3-4. Wiring of Multiple Inverters.

The inverter requires the installation of several ground connections, as shown in Figure 3-5.

Refer to the NEC for information regarding ground connections. The grounded electrode

conductor (GEC) is a conductor that connects the grounded electrode (also called a ground

rod) to the rest of the electrical grounding system. This point in the grounding system is

commonly located at the chassis of the AC power distribution panel (and the bonded neutral

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lead of the AC power source). The metal frames of all solar modules within the solar array,

including mounting racks, are normally connected to the grounding system through an

equipment grounding conductor (EGC). These conductors connect all exposed metal within

the power system to the grounding system, and electrically connect each chassis together,

including the string inverter, AC power distribution panel, and other circuit-breaker boxes,

junction boxes, combiner boxes, and utility (kWh) meters. Surge arrestors can be added to

the DC and AC parts of the system for additional equipment protection, but they do not protect

against a direct lightning strike.

Figure 3-5. Inverter Ground Connections.

Commonly used copper wire insulation colors for DC power are red for positive, white (or gray)

for negative (grounded), black for negative (ungrounded), and green (or green with one or more

2.


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Commissioning

•

• Check the polarity of all solar module wiring.

• Check all wiring and labeling for proper installation. Make sure that all electrical

connections and mechanical mounts are secure and weatherproofed.

• Ensure the job site is clean and safe.

•

are within the correct DC voltage range.

•

• Ensure the DC voltage ratings of the circuit protection and inverter input cannot be

exceeded under any circumstances.

• Check and enable the DC disconnect to apply power to the system.

• Check and enable the ground-fault protection.

• Check and enable the AC disconnect to energize the AC loads.

• If available on the string inverter, run the built-in diagnostic test to check for any system

problems, troubleshoot and repair any faults, and reset power.

Maintenance

AC sides of the inverter. The GFDI fuse and string fuses must be checked for proper continuity.

Any inverter cooling fans must be checked for proper operation and kept clean and free of

debris as well.

Utility-Interactive Software

data interface hardware and personal computer software. Digital data can be logged or stored

in computer memory for later analysis by computer programs that can display plotted data in

the form of graphs and charts. In addition, smart grid technology allows the utility company to

monitor energy usage of a residential home or commercial business. This data can be analyzed

and used to control electricity consumption and cost throughout the course of each day.

A typical data monitoring system is shown in Figure 3-6. The router permits digital data

communication between devices within a local area network (LAN) and can also allow

broadband access with a wide area network (WAN). A computer can provide the necessary

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data-logging (storage) function, in addition to any data analysis features that may be required

by the system user.

Figure 3-6. Monitoring System.

settings on string inverters and other data communication equipment. Often, remote displays or

the direct connection of sensor outputs.

Hardware and software monitoring tools can vary greatly between different equipment

manufacturers. Below is a list of some common makes and models that are readily available.

Hardware

•

•

•

Software

• Fronius USA SolarNet (solar.access and solar.web)

• SMA America Sunny (Design and Explorer) and Flashview

•


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Data acquisition equipment and sensors are used to record, process, store, retrieve, and

features that are commonly available in many of today’s data loggers and monitoring systems:

•

• Energy generation (kWh) – solar yield

• Energy usage (kWh)

• Energy cost savings ($)

• Carbon dioxide (CO2

• Environmental conditions (cell and ambient temperatures, wind speed, and solar irradiance)

The hardware interfaces for transferring the digital data to a computer or microprocessor

for storing, analyzing, and displaying the information can vary greatly. Here is a list of some

common data interfaces that are often available on string inverters, monitoring accessories, and

remote controls.

•

remote monitoring or remote control

• Infrared port (IrDA) for remote control

•

network (WAN)

• Modem port (RJ-11 jack) for transmitting data between the utility company and the

residential power system or sending SMS text messages

•

The latter three interfaces are wired, and require cables to be routed through electrical conduit

or wire trays to distribute the data signals.

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Figure 3-7. Remote Display.

Remote data acquisition and power management techniques use specialized computer

Many monitoring systems allow the collected data to be analyzed and displayed on the

Internet and on remote monitors, sent to mobile phones via SMS text messages and personal

computers via e-mail messages, and viewed on other portable wireless devices as well.

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The grid-tie training system consists of the following components. Study the schematic and the

list of parts in Appendices E and F. The explanations below provide a better understanding of

each item’s function or purpose.


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Mobile workstation

Figure 3-8. Model 46125 Workstation.

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Solar array simulator

manually operated with an adjustable control knob to simulate sunrise and sunset, and includes

a power switch, a power indicator, and meter-ready output test jacks. It is fuse-protected with a

Figure 3-9. Solar Array Simulator (Supplied Assembled).

DC combiner box

bus bar junction point that feeds the string inverter. A safety device is also wired into the box

Figure 3-10. DC Combiner Box.


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DC disconnect switch

and local electrical codes). The DC disconnect switch is shown in Figure 3-11.

Figure 3-11. DC Disconnect Switch.

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Sunny Boy string inverter

single-phase. It supplies this power to residential loads and to the utility grid (Figure 3-12). The

Figure 3-12. Sunny Boy SB 700U String Inverter.

AC disconnect switch

disconnect the Sunny Boy string inverter from the AC distribution panel per NEC and local

electrical codes (Figure 3-13). A safety device is also wired into the box called an AC lightning

arrestor.

Figure 3-13. AC Disconnect Switch.


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AC distribution panel—used to supply AC power to the residential loads. The panel is

installed with four breakers: one for the mains disconnect, one for the inverter disconnect, and

two arc-fault circuit interrupters (AFCIs) for branch load circuit disconnects.

Figure 3-14. AC Distribution Panel.

Residential load outlet boxes—used to plug AC loads and to show the excess power from the

Figure 3-15. Residential Load Outlet Boxes.

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Earth ground—connection is used to simulate the ground rod outside a home that grounds the

distribution panel to earth (Figure 3-16).

Figure 3-16. Earth Ground Connection.

Service entrance—used to bring the utility wires (in this case, from a wall outlet) into the

Figure 3-17. Service Entrance.


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Digital multimeter (DMM)

simulator to the input of the inverter.

Figure 3-18. Digital Multimeter (DMM).

Power/usage monitor—portable meter for monitoring AC voltage, current, power, and power

Figure 3-19. Power/Usage Monitor.

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Lockout/tagout device (with hasp) (2)

Figure 3-20. Lockout/Tagout with Hasp.

Light socket adapters (2)

(Figure 3-21).

Figure 3-21. Light Socket Adapter.


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AC incandescent lamp (2)

(Figure 3-22).

Figure 3-22. Incandescent Lamp.


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OBJECTIVES

In this job, you will identify and locate the many different components of the grid-tie

training system.

EQUIPMENT REQUIRED

Refer to the Equipment Utilization Chart in Appendix A to obtain the list of equipment

required for this job.

SAFETY PROCEDURES

Before proceeding with this job, complete the following checklist.

You are wearing safety glasses.

You are wearing safety shoes.

You are not wearing anything that might get caught such as a tie, jewelry, or

loose clothes.

If your hair is long, tie it out of the way.

The working area is clean and free of oil.

Your sleeves are rolled up.

Instructor initials:

PROCEDURE

Utilization Chart in Appendix A.

points and electrical ground points of each component, in addition to

any mechanical interfacing between the various devices. Refer to the

schematic diagrams provided in Appendix E.

a sealable plastic bag and label the bag with the part number found in

Appendix A.

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Name: _________________________________ Date: ______________________

Instructor approval: ___________________________________________________

If the components are already in storage bags, remove the components

NOTE: You will take the trainer apart after all procedures within the entire Grid-Tie Training System curriculum have been completed. The components must be returned to the storage bags and placed in an area designated by the instructor.

If you are having trouble locating or identifying any components, ask

your instructor for assistance.

Ask your instructor to check and approve your work.

Date post:	07-Jul-2018
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Job Sheet 3 – Trainer Components - Lab-Volt · Job Sheet 3 – Trainer Components ... A...

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