This cable-segregation scheme divides the network by voltage and service. Apply the stated separation rules to main routes, field branches, crossings, and cable entries at compact equipment. The evidence does not define measurement reference points, tray-divider requirements, or signal-compatibility criteria; resolve those items in the project design before installation.
Cable system classification
| System | Cable service | Defined boundary |
|---|---|---|
| System 1 | High-voltage systems | Above 1000 V |
| System 2 | Low-voltage power supply and electrical control cables | 1000 V and below |
| System 3 | Instrumentation and telecommunication systems | No voltage boundary stated |
Classify every cable before assigning its support system. The 1000 V boundary separates System 1 from System 2; instrumentation and telecommunication function defines System 3.
Routing System 2 and System 3 cables
Instrumentation and telecommunication cables may use System 2 cable supports when installers maintain at least 300 mm between the individual systems. The evidence does not specify whether to measure this distance between cable surfaces, bundles, or support-system edges, so record the project-approved reference before routing.
System 2 and System 3 cables may share the same field tray only on the branch from the main route to a single item of equipment and only when the cable signal types do not conflict. Because no compatibility matrix is supplied, review the actual signal types rather than treating this branch allowance as unconditional.
Crossings, equipment entries, and IS routing
A right-angle crossing is acceptable without additional segregation. Preserve the applicable segregation when cables enter or leave field equipment, including small packages, minor modules, and crane pedestals; limited space at the termination does not cancel the routing rules.
Route intrinsically safe (IS) and non-intrinsically safe (non-IS) instrument cables on the same cable ladders or trays under this scheme. When both cable groups have armour and screens, they may be tied together in the same bundle. The evidence does not address arrangements where either group lacks armour or a screen, so do not extend the bundling permission to that case without project clarification.
Installation and verification procedure
- Assign each cable to System 1, System 2, or System 3 using its voltage and service.
- Keep System 3 cables on their own support, or verify and maintain the 300 mm minimum when using System 2 supports.
- Before combining System 2 and System 3 on a field tray, confirm that the route is a branch to one equipment item and that the signal types do not conflict.
- Arrange unavoidable crossings at right angles; no further segregation is required at that crossing.
- Inspect cable approaches and departures at packages, modules, crane pedestals, and other field equipment for continuity of the required segregation.
- For a common IS/non-IS bundle, verify that both groups contain armour and screens before tying them together.
FAQ
Can instrumentation cables run on a low-voltage power cable support?
Yes. System 3 instrumentation and telecommunication cables may run on a System 2 support when a minimum distance of 300 mm is maintained between the systems.
Do power and instrument cables need separation when they cross?
A right-angle crossing is acceptable without further segregation. This exception applies to the crossing and does not remove the separation requirements along parallel routes.
Can IS and non-IS instrument cables be tied in one bundle?
Yes, under the stated scheme, when both the IS and non-IS cables contain armour and screens. If either group lacks armour or a screen, the evidence provides no bundling rule and project clarification is required.
