In brief. An industrial solar plant is an engineering asset: a project built around your consumption profile, switchboard equipment, and correct connection to the electrical grid. The quality of the project determines how much the plant actually generates, how it behaves under fault conditions, and whether new technical conditions are needed at all. Below is what's included in the project, which documents are needed, and how grid connection works. One key point up front: the project scope and the list of permits depend on the plant's capacity and its connection method — what's mandatory for a multi-megawatt station may not be needed at all for a 50 kW rooftop plant under self-consumption.

Why you need a project

An industrial solar plant is designed around the site's real load profile, not on the principle of "however many panels fit." The project determines generation capacity relative to your consumption, the connection point and voltage class (0.4 / 6 / 10 / 35 kV), the single-line diagram, and the method of protection under fault conditions. Both the energy yield and safety — and whether you need to change the site's contracted capacity at all — depend on these decisions.

Two typical configurations — and why this determines everything else

Before talking about documents, it's worth being upfront about two scenarios. In most cases, it's the plant's capacity and connection method that determine how much paperwork and what equipment you'll need.

Scenario A — a solar plant for self-consumption, within already-permitted capacity. The plant (for example, a 30–150 kW rooftop system) connects to the site's internal network and works mainly to cover self-consumption. If the generation capacity doesn't take you beyond the site's already-permitted (contracted) capacity, new technical conditions for increasing connection capacity are generally not required — you aren't changing the parameters of your connection to the operator's grid, you're adding generation within your own installation. Protective functions in this scheme are handled by the grid-tie inverter (more on this below).

Scenario B — a large plant or a separate generation connection. If the solar plant's capacity exceeds the site's permitted capacity, or the generation connects separately (a primary/separate connection, roughly from a few hundred kW) — then you need technical conditions (TU) for connection, a connection project, a switchgear installation of the appropriate voltage class, a separate relay-protection complex, and a power-evacuation line. This is the "heavy" scope, and it's justified specifically for such sites — not for every solar plant.

Correctly assigning your site to one of the two scenarios is the project's first engineering decision. A mistake here costs you either unnecessary approvals that could have been avoided, or, conversely, an attempt to "squeeze through" without the technical conditions that are actually mandatory.

Solar plant project scope

The base package the customer receives:

Technical specification (TS) — built around your site and consumption profile.
Single-line diagram — how the plant connects to the site's internal network (and, for Scenario B, to the operator's grid as well).
Working documentation — module layout, cable routes, support structures, grounding, lightning protection.
Switchboard equipment — specification and diagrams. At LK, this is our own manufacturing: from 0.4 kV assemblies to packaged substations (КТП) and 10/35 kV switchgear.

What's added only when needed (mainly Scenario B or large sites):

10/35 kV switchgear installation and power-evacuation line — when there's a separate connection of generation to the operator's grid.
Separate relay-protection complex — for plants with a power-evacuation line (roughly from a few hundred kW).
Environmental impact assessment section — when the site's parameters fall under the relevant requirements; generally not needed for small rooftop plants.

This package is what constitutes a "solar plant project." The package scope scales with capacity: the larger the site and the closer it is to a separate grid connection, the more sections it requires.

Protection under fault conditions: inverter or separate relay protection

This is where many texts mix up small and large plants, so let's be precise.

For small solar plants under self-consumption, connected to the internal network, the key protective functions are handled by the grid-tie inverter. It implements anti-islanding protection and automatically disconnects generation when grid voltage disappears or deviates — per international requirements for grid-tie inverters (EN 50549, IEC 62116). In plain terms: if voltage disappears on the operator's grid, the inverter doesn't "feed" the de-energized line — this protects both grid personnel and the equipment itself. Separate relay protection is generally not needed in this scheme.

A separate relay-protection complex (RZA) appears on larger plants — where there is a power-evacuation line into the operator's grid (roughly from a few hundred kW, or with a separate generation connection). Here, protection is built on relay devices at the switchgear installation, not on the inverter alone.

So the correct formulation is: the protection scope depends on whether the plant has a power-evacuation line into the operator's grid. Attributing full relay protection to every 50 kW rooftop solar plant is engineering-wise incorrect.

Which documents and permits are needed

The list depends on the scenario (A or B) and capacity. General guideline:

Always: title documents for the site or roof; project documentation (scope above).
For Scenario B (exceeding permitted capacity or a separate generation connection): technical conditions (TU) for connection from the distribution system operator (DSO), a connection project, approvals; if needed — an expert review and an environmental impact assessment section.
For Scenario A (within permitted capacity, for self-consumption): new TU for increasing connection capacity are generally not needed; instead, if you plan to sell surpluses to the grid, active-consumer status is arranged (see the next section).

The list isn't universal, so it's always clarified at the outset for your specific site — so you don't find out during installation that something's missing (or that you ordered unnecessarily heavy procedures).

Grid connection and active-consumer status

The procedure differs for the two scenarios.

Scenario B (separate connection / capacity increase): 1. Connection application → technical conditions (TU) from the operator. 2. Connection project and approvals. 3. Construction and installation works, testing, commissioning. 4. Entry into operation.

Scenario A (within permitted capacity, selling surpluses — active consumer): Active-consumer status under the self-generation mechanism (net-billing) is arranged without separate technical conditions, if the plant fits within the permitted capacity. Key steps: - A self-generation electricity purchase-sale contract is concluded — it is an addendum to the electricity supply contract (with the supplier, including a universal-service supplier). - Bidirectional (two-way) commercial metering is installed, which separately measures consumption from the grid and feed-in to the grid. - The distribution system operator checks that the equipment and metering comply.

A separate licence to sell surpluses is not needed — this is a fundamental difference between net-billing and the "green tariff" of past years. Important: net-billing is compensation for the value of the energy, not a guaranteed income. It's a matter of offsetting the value of the energy fed into the grid against your settlements with the supplier, not a fixed payment. In addition, for non-household active consumers, the volume of feed-in to the grid is regulated — generally up to 50% of the permitted capacity; the exact conditions depend on the consumer category and are checked against current rules for your site. So feed-in to the grid isn't unlimited — one more argument for sizing the plant around self-consumption.

Important in both scenarios: the decision on issuing TU and the connection volume rests with the operator. The contractor prepares the full package and runs the process, but cannot guarantee the operator's decision — that's outside its area of responsibility.

Design standards

Solar plant design relies on current building codes and industry rules (electrical installations, grounding and lightning protection, fire safety), while the operation of grid-tie inverters relies on dedicated standards for connecting generation to the grid (EN 50549 / IEC 62116). Compliance with these standards is a condition both for passing approvals and for safe plant operation. The engineer builds the specific current editions of the standards into the project for your site.

Standard or custom project

Standard solutions (for example, packaged substations (КТП) for solar plants, standard switchboard assemblies) speed up and reduce the cost of the project. But capacity, connection method, and protection scope are always calculated for the specific site. A "ready-made project from the internet," without being tied to your site, consumption profile, and connection parameters, won't pass approvals and won't match the actual plant.

Where to start

For an assessment, we need: capacity or site area, site type (roof/ground), consumption profile, the site's permitted (contracted) capacity, and the input voltage class. Based on this data, we immediately see which scenario (A or B) applies to your site, and prepare a TS and an indicative estimate.

→ Order a project or calculation for your site. Or download the checklist "How to choose an industrial solar plant contractor."

Frequently asked questions

Are technical conditions (TU) required for an industrial solar plant? Not always. If the plant is for self-consumption and fits within the site's already-permitted (contracted) capacity, and connects to the internal network, new TU for increasing connection capacity are generally not needed. TU are needed when the solar plant's capacity exceeds the permitted capacity or when the generation connects separately. This is determined at the outset based on your site's parameters.

How do I start selling surpluses — and is a licence needed? Through active-consumer status under the self-generation mechanism (net-billing). No licence is needed. A self-generation purchase-sale contract is concluded (an addendum to the supply contract), and bidirectional commercial metering is installed. Net-billing compensates the value of the energy fed in — it is not a guaranteed income.

Does a solar plant need separate relay protection? Depends on capacity and connection method. For small plants under self-consumption, protective functions (including anti-islanding) are handled by the grid-tie inverter. A separate relay-protection complex is needed for larger plants with a power-evacuation line into the operator's grid.

How long does connection take? For the separate-connection scenario, it depends on the voltage class and the operator's queue; we provide an indicative schedule after receiving the TU. For self-consumption plants within permitted capacity, the procedure is shorter, since new TU are generally not needed.

Can I use a standard project? Standard components (КТП, switchboard assemblies) — yes; but capacity, connection, and protection scope are calculated for your specific site.

Industrial solar power plant project: what's included and which documents you need