Factory Electrical Projects in an OIZ: What to Watch For

For an investor setting up a factory in one of Bursa's 17 organized industrial zones (OIZ), an electrical project doesn't stop at complying with the general EKAT regulation and the relevant TS/IEC standards. Each OIZ has its own technical specification, its own medium-voltage network, and its own approval process — an additional layer on top of general legislation. A factory project can be flawless by general-regulation standards and still get stuck at site approval, sent back for revision, and delay energization by weeks if it doesn't match the specific OIZ's specification. This guide explains how OIZ-specific requirements differ from general legislation, why each OIZ imposes its own format, and how a factory project must be coordinated with the OIZ's own MV network.

What Is an OIZ Technical Specification, and Why Does It Exist?

Every organized industrial zone operates its own electrical distribution infrastructure, with its own MV network topology, substation standards, and protection philosophy. Because of this, OIZ management bodies publish an additional technical specification for every facility built within their boundaries. This specification goes beyond general legislation on matters such as acceptable transformer power, cell types, cable routing rules, meter placement, protection relay setting ranges, and sometimes even manufacturer restrictions. While general legislation (EKAT and the relevant TS/IEC standards) defines minimum safety and technical adequacy, the OIZ specification adds a facility-specific layer that says "in this zone, it's done this way."

Why Does Each OIZ Demand a Different Format?

Each of Bursa's 17 OIZs was established in a different year, with different MV network infrastructure, different substation capacity, and a different operating history. One OIZ's network might run as a ring topology while another runs radial; one might have standardized on a particular brand of switchgear while another is built around a different equipment family. These differences lead each OIZ management to develop its own technical specification, shaped by its own operating experience. As a result, even two similarly sized factories in two neighboring OIZs can end up with noticeably different electrical projects — especially in MV connection cell design, transformer type, and protection coordination settings. Submitting a project template prepared for one OIZ directly to another, without revision, almost always results in rejection or a request for revision.

Where Does an OIZ Specification Diverge From General Regulation?

The differences encountered most often on site fall into these categories:

• Transformer power and type restrictions: some OIZs require a separate MV cell or a specific connection scheme above a certain power threshold; others mandate dry-type transformers.
• MV cell type and manufacturer compatibility: the OIZ may require a cell compatible with the switchgear family used in its own network, for maintenance and spare-parts standardization.
• Protection relay setting ranges: to ensure selectivity between the OIZ's main breaker and the facility's incoming breaker, specific relay setting ranges or curve types may be mandated.
• Metering and communication standards: the OIZ may require a specific meter brand or communication protocol that integrates with its own energy management system.
• Cable routing and crossing points: existing cable routes, road crossings, and shared ducts within the OIZ's infrastructure can constrain the routing of the factory's incoming MV cable.

Coordinating the Factory Project With the OIZ's MV Network

A factory's own substation project doesn't exist in a vacuum — it connects into the OIZ's MV network at a specific point, and it must be compatible with the short-circuit power, voltage level, and protection philosophy at that point. The typical failure points in this coordination are:

1. Short-circuit power mismatch: the factory's short-circuit calculation must be based on the short-circuit power the OIZ actually provides at the connection point; calculations done without formally requesting this data from the OIZ tend to deviate from the real value.
2. Selectivity mismatch: if the incoming breaker's protection settings aren't coordinated with the OIZ's main feeder breaker in time and current grading, a minor fault inside the factory can trip the OIZ's upstream breaker — turning into a wide outage affecting not just that factory but neighboring facilities on the same feeder.
3. Voltage level and connection scheme compatibility: the MV voltage level the OIZ operates at (such as 34.5 kV) and its connection scheme (radial, ring, star) directly determine the incoming cell design of the factory's substation project.
4. Load forecast and capacity reservation: the OIZ reserves capacity across its network based on the installed power each factory declares; if a factory later expands its power draw, that requires a separate coordination process with the OIZ.

How Does a Typical OIZ Approval Process Work?

A factory electrical project inside an OIZ typically moves through these stages: first, the OIZ's technical specification and current MV network data (connection point, short-circuit power, voltage level) are obtained; the project is prepared based on this data; it's submitted to the OIZ's relevant technical unit (usually its infrastructure or electrical directorate); the OIZ's own engineers review it against the specification and provide feedback; revisions are made; and the approved project is folded into the general approval process submitted to the utility and relevant official authorities. This two-layer structure — OIZ approval first, then utility/official approval — can extend the overall timeline; a project prepared without knowing OIZ-specific requirements up front risks being revised twice. We cover how the general approval process works in our project approval guide.

Common OIZ-Specific Approval Pitfalls

• Calculating with outdated MV network data: an OIZ's network expands or gets reconfigured over time; a calculation based on an old short-circuit power figure may not reflect current conditions and gets rejected at approval.
• Ignoring the OIZ's switchgear/equipment standard: a cell selection that meets general legislation but is incompatible with the OIZ's preferred equipment family gets returned during technical review as "non-standard."
• Leaving metering and communication integration out of the project: some OIZs want to see meter communication infrastructure at the project stage; leaving this detail to the field gets flagged as a deficiency during site inspection.
• Evaluating selectivity coordination only within the facility: even if internal coordination is done correctly, if it isn't checked against the OIZ's upstream breaker, the project can be sent back as "incompatible with the OIZ's main network."
• Confusing OIZ approval with utility approval: some investors assume the process is complete once OIZ approval is obtained, but OIZ approval does not replace the separate approval processes run by the utility and official authorities.

The Impact of Capacity Expansions and Later Modifications

A factory may want to expand production and increase transformer power years after initial setup. In that case, the project affects not just the factory's own electrical infrastructure but the OIZ's overall capacity planning on that feeder. Because the OIZ sizes its substations and MV lines based on the sum of installed power declared by all facilities in the zone, later expansions may be subject to OIZ approval and sometimes network reinforcement work. For projects with a planned capacity increase, engaging the OIZ early both shortens the approval timeline and reduces the risk of an unexpected network constraint on site.

OIZ Influence on Substation Design

The factory's own substation design is also directly shaped by the OIZ's specification — decisions such as cell count, instrument transformer accuracy class, earthing system type (TN, TT), and even whether the substation is indoor or outdoor must align with the OIZ's standard practices. We cover the general substation setup process in our substation setup guide; for a substation built inside an OIZ, that general process must be evaluated together with the OIZ's additional requirements.

The Value of Early Communication With the OIZ

For an experienced project team, the single most time-saving step is a short pre-consultation with the OIZ's technical unit before the project begins, clarifying current MV network data, the preferred equipment standard, and any recently changed specification clauses. Skip this and prepare the project purely off general legislation, and the mismatches that surface during the OIZ's technical review can force a redesign spanning everything from cell selection to protection settings. Firms investing in multiple OIZs at once get far more reliable results tracking each zone's specification separately than pushing one standardized template across all of them.

Practical Sequence for Preparing an OIZ Electrical Project

1. Formally obtain the target OIZ's current technical specification and MV network connection data.
2. Shape transformer power, cell type, and earthing system choices around the OIZ's standard practices.
3. Perform the short-circuit calculation using current network data obtained from the OIZ.
4. Evaluate protection coordination not just within the facility but together with the OIZ's main breaker.
5. Build metering and communication systems into the project to the OIZ's required standard.
6. Submit the project to the OIZ first, then to the utility and official authorities — plan the two processes sequentially, not in parallel.

Common Mistakes

• Learning the OIZ's specification at the approval stage instead of before the project starts: this can force a large part of the project to be redrawn.
• Reusing a project prepared for a different OIZ without revision: since every OIZ has its own requirements, this approach almost always gets rejected.
• Treating OIZ approval as final approval: OIZ approval does not replace the separate approval steps run by the utility and official authorities; the process is sequential.
• Not informing the OIZ of capacity expansion plans in advance: later expansion requests can run into the OIZ's network capacity constraints.
• Ignoring the OIZ's preferred equipment standard: equipment choices that meet general legislation but conflict with the OIZ standard are grounds for rejection during site review.

FAQ

Does an OIZ's technical specification replace the general electrical regulation? No. The OIZ specification is an additional layer on top of general legislation (EKAT and the relevant TS/IEC standards); minimum safety and technical requirements come from general legislation, while OIZ-specific details come from the specification.

Is every OIZ's specification the same? No. Each OIZ applies a different specification based on its own MV network infrastructure, equipment standard, and operating experience; a project prepared for one OIZ cannot be applied directly to another.

Is another approval needed after OIZ approval is obtained? Yes. OIZ approval does not replace the separate approval processes run by the utility and relevant official authorities; these processes follow one after another.

What data should be obtained from the OIZ for the factory's short-circuit calculation? Data such as short-circuit power at the connection point, voltage level, and, where applicable, the OIZ's protection setting philosophy should be formally requested from the OIZ.

Can a factory's transformer power be increased later within an OIZ? It's possible, but since it can affect the OIZ's overall capacity planning in the zone, the change should be reported to the OIZ and resubmitted for approval if necessary.

What happens if a project doesn't meet the OIZ specification? It gets returned or sent back for revision during technical review, which delays the energization date.

Why can two neighboring factories' projects differ from each other? Even within the same OIZ, differing power needs, connection points, or establishment dates can mean different specification details and MV network conditions apply.

Who should prepare an OIZ electrical project? An EMO-registered electrical engineer familiar with OIZs' technical specification practices, who can revise the project according to the OIZ's official approval process.

Conclusion

Preparing a factory electrical project inside an OIZ requires more than complying with general legislation — every OIZ has its own technical specification, MV network structure, and approval process. A project that doesn't account for this layer from the outset can get stuck at OIZ approval even if technically correct, delaying energization. For a team that has developed projects across Bursa's 17 OIZs over the years, knowing these differences in advance is the most reliable way to get a project through approval on the first pass.