Grounding is crucial for the safety and proper functioning of PV systems. These systems can be either grounded or ungrounded, depending on the application, to prevent electrical shocks and ensure effective operation. In this blog, we’ll walk you through the major differences between grounded vs. ungrounded PV systems.
Grounded Vs. Ungrounded PV Systems
Grounded and ungrounded photovoltaic (PV) systems differ in design, implementation, and associated risks and benefits. Before comparing them, let’s explore each system in detail.
What are Grounded Systems?
These systems have a grounded conductor required by NEC Section 250-23(b) to run to each service disconnecting means. This grounded conductor can serve as a current-carrying conductor for all neutral-related loads and also as an equipment grounding conductor to clear ground faults per NEC Section 250-61.
A system is considered grounded if the supplying source, like a transformer or generator, is grounded. The neutrality of any grounded system serves two main purposes:
- Allowing the use of line-to-neutral voltage and serving as a current-carrying conductor for unbalanced current.
- Providing a low-impedance path for fault currents to enable the operation of overcurrent devices in the circuit.
What is an Ungrounded System?
Ungrounded systems are not entirely without a connection to the ground. Electrically, your system is linked to the ground through capacitance between the lines and the earth. It’s more accurate to call it a capacitance-grounded system. However, it’s conventionally referred to as an ungrounded system because there is no intended physical connection between the powerlines and the ground.
In simple terms, in an ungrounded system, the ground-fault current is minimal, reducing the risk of shock to people. During a fault, two wires are necessary to carry some currents, preventing excess voltage that can cause heat and equipment damage. However, since ground fault is minimal, locating faults can be challenging and time-consuming, making the overall cost of ungrounded systems quite high.
Now that you know both types of electrical grounding for PV systems, let’s also go through a table highlighting the difference between grounded and ungrounded PV systems.
| Characteristics | Grounded PV Systems | Ungrounded PV Systems |
| Physical connection between powerlines and the ground | Have a grounded conductor that serves as current-carrying conductor and equipment grounding conductor | Linked to the ground through capacitance between the lines and the earth |
| Connection to Ground | 1 necessary connection from either the positive or negative side | No necessary connections from either bus |
| Regions where commonly used | North America | Europe and Asia |
| Grounded Circuit Conductor Requirement | Required | Not required |
| Ground-Fault Protection | Protects against issues like arc-flash, shock hazards, equipment damage, fires | Less protection from trips due to capacitance, related to PV system size |
While both grounded and ungrounded PV systems can offer equal safety levels, grounded systems provide better ground-fault protection and are less susceptible to nuisance trips.
Also Read: 3 Leading Types Of Solar PV System
Grounded Vs. Ungrounded PV Systems Price
Ungrounded systems are not significantly different from grounded systems, as they still utilize equipment-grounding conductors connecting module racks, combiner enclosures, disconnects, and inverters together and to the ground. The cost of grounded versus ungrounded PV systems may vary based on the specific components used. However, ungrounded systems might be less expensive due to their simpler installation process and the absence of a grounded circuit conductor requirement.
What is a Functionally Grounded PV System?
A functionally grounded PV system is a solar electric system that has an electrical ground reference to the ground for operational purposes but is not solidly grounded.
Also See: How to Ground Solar Inverter
What is a Negative Grounded PV System?
A negative grounded PV system is a solar electric system where the negative terminal of the PV solar power array is connected to the ground. This connection is made through conductive materials like a fuse, circuit breaker, resistance device, non-isolated grounded AC circuit, or an electronic means within an inverter or charge controller. Negative grounding in solar inverters improves the overall performance of the solar power system by reducing electrical noise and interference, ensuring the smooth functioning of the inverter and the solar system.
Grounded Vs. Ungrounded PV Systems: Which to Choose and When?
Both grounded and ungrounded PV systems provide unique benefits, and the decision between them depends on local regulations, safety needs, and system design. However, grounded systems, common in North America, offer better fault protection but may have more complex operations. On the other hand. ungrounded systems, prevalent in Europe and Asia, rely on capacitance and might be less expensive due to no grounded conductor requirement.
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