> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/deployment-resources/security-and-compliance/perimeter-fence-compliance/critical-distances-reference.md).

# Critical Distances Reference

Check required clearances between pulse fences, barriers, power lines, and hostile toppings.

### This page answers

* What separation is required between the pulse fence and a physical barrier?
* What are the market-specific barrier rules?
* What clearances apply near power lines and hostile toppings?

### Attached Fence (to physical barrier)

* Minimum separation: 100mm (4in)
* Maximum separation: 200mm (8in)
* OR minimum 1000mm (39in) where barrier openings are over 130mm (5in)
* Where an attached or free-standing barrier has **no openings**: maximum 200mm (8in) or minimum 1000mm (39in)

#### Market-Specific Barrier Rules (INTCOP 4.5)

| Market             | Standard    | Rule                                                                                                     |
| ------------------ | ----------- | -------------------------------------------------------------------------------------------------------- |
| UK (Palisade)      | BS1722-17   | 100 to 200mm (4 to 8in) separation, or 1000mm (39in) min where any opening dimension is over 130mm (5in) |
| NZ/AU (Chain Mesh) | AS/NZS 3016 | 1000mm (39in) min where any opening dimension is over 54mm (about 2in)                                   |
| Non-specified      | —           | 100 to 200mm (4 to 8in) separation, or 1000mm (39in) min                                                 |

{% hint style="info" %}
When selecting barrier type, consider the likely presence of young children. This affects acceptable opening sizes.
{% endhint %}

### Free Standing

* Minimum 1000mm (39in) from any structure
* Prohibited zone: energised conductors shall not be installed within the prohibited zone (the arc from top of physical barrier to ground on the public side, see INTCOP 7.1 Figure 1)

### Horizontal Separation (independent energisers)

* Minimum 2.5m between uninsulated pulsed conductors from different unsynchronised energisers

### Vertical Separation

* Minimum 2m between pulsed conductors from different unsynchronised energisers

### Power Lines

| Voltage       | Min separation |
| ------------- | -------------- |
| 1000V or less | 3m (9ft 10in)  |
| 1000V to 33kV | 4m (13ft 1in)  |
| Over 33kV     | 8m (26ft 3in)  |

#### Near Overhead Power Lines (INTCOP 4.5.1)

* Fence conductors **shall not** be mounted on overhead power-line support structures
* Where crossing overhead lines is unavoidable: cross underneath, at right angles, as close to the lines as possible
* Connecting leads and fence wires near an overhead power line shall not exceed **3m (9ft 10in)** above ground
* This height limit applies within the orthogonal projection of the outermost power conductors for a distance of:
  * **2m (6ft 7in)** for power lines 1000V or less
  * **15m (49ft 3in)** for power lines over 1000V
* Where a fence passes below **bare** power conductors: the highest metallic element shall be earthed for **not less than 5m (16ft 5in)** on either side of the crossing point

### Barbed / Razor Wire Proximity

* Energised barbed or razor wire is **prohibited**
* Non-energised barbed or razor wire near an energised fence: minimum **1m (3ft 4in)** horizontal reach distance to prevent simultaneous contact with both

***

🔗 **Related**

* International Code of Practice (INTCOP 7.1) · Warning Sign Requirements


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