FAQ

ALL ABOUT CABLE DETECTION

1What is cable detection?

Cable detection is a process of determining the existence of underground utilities by using specialized equipment to pick up signals that may naturally radiate from buried conductors.

2Why do we do need to do cable detection?

Buried utilities can be uniquely complex in the underground environment.  These utilities must be protected with greater security in terms of supply and distribution. It is a requirement under the Electricity Act and Telecommunication Act that all contractors need to engage a Licensed Cable Detection Worker (LCDW) & Telecommunication Cable Detection Worker (TCDW) to ascertain the location of high voltage cables in the work area before starting earthworks. 

3Can cable detection reveal the cable voltage, size or quantity?

Site detection only picks up signals from the ground.  Cable details such as voltage type, size and quantity can only be retrieved from as-built drawings or literally observed from exposed utilities in trial holes/trenches.

4What do you need before you can do the detection?

We need the latest copy of topography survey in AutoCAD format, a detection drawing preferably with all site features captured and a decent site layout plan.

 
5Can you tell if the cable is alive or dead?

Detection instruments only picks up signals which is not a deciding factor to confirm if the cable is dead or alive. One can engage a Qualified Cable Jointer to do cable testing however the results may not be conclusive as well. As the status of any particular cable can be changed by its owner, it is best to seek the status of any cable from the owner directly.  

6Can you tell the depth of the utility by detection?

Cables in general, except sewer, are laid 1 to 2m below ground level. They are laid deep enough to avoid any interference from the imposed weight of passing vehicles and also at a level catered for routine maintenance. As grounds may be topped up or trimmed off subject to earthworks carried out from time to time, it is not possible to tell the depth of the utilities by detection.

* Sewer lines are laid at a gradient with free gravity flow, it can be at 10m or deeper.

* Extra high voltage cables are usually laid deeper than the normal utilities. Beyond this depth are deep tunnel sewers and cable tunnels.

7I know there is an 800mm diameter water pipe within my site, can it be easily detected?

It depends. Some pipes can be picked up by a receiver alone while others may need signal injection to detect it. The level of detection is highly sensitive and it is dependent on site condition and its surrounding environment.

8Why do we see multiple cables when there is only one cable shown on the detection drawing?

The detection drawing indicates the cable but not the number of cables for that area. It is possible that some other utilities which were not picked up by signals are also sitting within the vicinity of the same cable route.

9What are the factors affecting site detection?

There can be many factors affecting the results of site detection.

The primary factor is the signal strength of the target line. The signal must be strong enough for the instrument to pick up at ground surface. Its surrounding soil type, underground water table, salinity, the conductivity of the utility, etc play a decisive factor for a successful report. 

Also, not all the utilities are detectable or can be easily detected. Eg. Ductile iron pipes are joint by spigot / socket with a rubber gasket. As the metal parts of such pipes are not in contact with each other, this makes detection very challenging as there is no conductivity of the whole pipeline.


10What are the challenges in site detection?

In an underground environment there are different types of soil, underground water tables, salinity and the conductivity of the utilities, etc. Detection is carried out at vast land area often with overgrown and unknown complexity.

The job become tougher especially in areas where multiple signals of buried cables in close proximity are picked up irrespective of the one you are hoping to detect.


Scenario 1 – Utility is not detectable due to overcast signal




Scenario 2 – Utility is not detectable due to weak signal


11Can my Sub-Contractor use your Detection Report?

No. Sub-Contractors should not use any Detection Reports that are not issued to them as there is no legal rights or protection if any unfortunate incident should happen.

12Under what circumstances is a re-detection required?

A re-detection may be required for some of the following scenarios below:

  • After the completion of cable diversion, and there’s a need to check further for live cables.
  • There were new services laid in the areas detected.
  • The existing road furniture in reference is removed, shifted and/or displaced.
  • Detection markings were not visibly recognizable due to weather or other site activities.

ALL ABOUT PUBLIC UTILITIES

1How many Public Utility Providers are there

There are 25 utility providers, namely:

  • SP PowerGrid
  • SingTel
  • StarHub Cable Vision
  • StarHub
  • SP Telecom
  • BlueTel
  • Flag Telecom
  • Global Transit
  • M1
  • Matrix Network
  • Netlink Trust
  • Orange Carriers
  • Reach Telecom
  • Sparkle
  • SuperInternet
  • Superloop
  • SuperSea
  • Tata
  • Telin
  • Telstra Global (PacNet)
  • Verizon
  • ViewQuest
  • PUB Water
  • PowerGas
  • PUB Sewer
2What are the information required for purchasing of the Utility Plans?

The following information are required when requesting for service plans

  • Lot Information of project site (Lot No.)
  • Plan Type (Service Plan for drainage/sewerage/water)
  • Requestor Details
3How long does it take to purchase utility plans?

It may take 1 to 4 weeks.

4How many types of cables are there?

The main types of cables are:

  • Low voltage cable in single phase – 230 volt
  • Low voltage cable in 3 phases (red, yellow and blue phase) – 415 volt
  • High voltage cable – 6P6kv (6,600 volt)
  • High voltage cable – 22kv (22,000 volt)
  • Extra high voltage cable (EHV) – 66kv (66,000 volt)
  • Extra high voltage cable (EHV) – 230kv (230,000 volt)
  • Extra high voltage cable (EHV) – 400kv (400,000 volt)
5How many cable types are there?

By their construction, there are oil filled / non-oil filled type; single core or multiple cores.

By their material, there are copper and aluminum.

By their insulation type, there are paper insulated and XLPE insulated cables.

6What are the colors of the cables?

The cables are generally black in color except 6p6kv is green and 22kv red. The latter may gradually fade/change and look a little black after some time.

7Are high voltage cables generally bigger in size than low voltage ones?

No. E.g. most cables are of 75mm in diameter. High voltage cables in airfield is only 15mm in diameter.

8What are cable slabs?

Cable slabs are labels that are placed directly above the buried cables to provide visible markings for their underlying utilities. Used to come in red bricks in the early years, cable slabs are mostly concrete or in PVCs nowadays.

9How do you tell the difference between a High and Low Voltage cable?
  • Low voltage cables can be identified as:
    Under red bricks with wordings like “SCC’, ‘SMC’, “PUB” or “public lighting”.
    Under black PVC cable slabs with relevant wordings.
  • High voltage cables can be identified as:
    Under concrete slabs with wordings like “EHT” and under yellow PVC slabs.
  • Extra High voltage cables can be identified as:
    Under concrete slabs with wordings like “EHV”, “66KV”, “230KV”, “400KV”.

* Pilot Cables or small cables up to 25mm in diameter that function as control, monitoring or communication may be laid alongside HV or EHV cables.

10Is there any change about cables were laid within PVC pipes?

Yes, besides using a direct buried method, cables can be laid within PVC pipes with draw pits/manholes at certain distant interval.

Power cables are of larger size (usually 150mm diameter) and communication cables in 100mm diameter. Smaller diameter tubes could be pulled into bigger pipes we call sub ducts which are mainly communication cables.

11What are the different types of underground utilities?
  • For electricity: cable of 150mm / 100mm in diameter, usually sit under cable slabs for easy identification.
  • For water: steel, cast iron, ductile iron, copper, stainless steel or PVC.
  • For gas: steel, cast iron, ductile iron, copper, stainless steel or PVC.
  • For gas: galvanized iron, cast iron, ductile iron, stainless steel or HDPE.
  • For sewer: stoneware, PVC, cast iron, ductile iron or concrete.
12What is a cable joint?

A complex cable network is laid using multiple cables that may run beyond certain lengths or road contours to cater to different site conditions. Cable joints are the intersection points between two connecting cables.

13What should I do when there is a cable joint nearby?

The joints are the weakest part of the cable network and are most vulnerable to damage. You should take special attention for works at cable joints to avoid any earth movement that may potentially damage this part of the cable network.

TRIAL HOLE / TRENCH

1What is the purpose of the trial holes?

The purpose of a trial hole is a pit for inspecting the existence and position of underlying utilities within that pit hole. We gather information like cable depth, size and quantity of these utilities exposed from these trial holes, prior to doing any excavation works.

2What is NCE for?

Under the Electricity Act and Gas Act and Telecommunication Act, any person who carries out earthworks in the vicinity of high voltage underground electricity cables or gas pipes, is required to obtain information of the existing electricity cables or gas pipes, engage a Licensed Cable Detection Worker to carry out cable detection and notify SP by submitting NCE no less than 7 days prior to the commencement of earthworks. This is to avoid any damage to the electricity cables and gas pipes.

3What does Earthwork mean?

Earthwork refers to the removal or excavation of existing earth material and any placement of fill material required for constructing the embankment.

4I intend to do some trial holes, do I require any NCE?

Yes. Any form of earth removal or ground penetration including trial hole must have a valid NCE. The type of NCE required is dependent on the available utilities for that locality.

5When can I commence my earthwork on site?

As soon as the NCE application is approved.

6How do you dig trial holes?

Trial holes are either dug manually or excavated using mini-excavator/breaker depending on site conditions. Site records like photos and trial hole dimensions are recorded prior to backfill,

7Can I remove the cable slabs to check the cables under it?

You can remove these slabs with the written approval from SP PowerGrid. Any unauthorized removal is considered as vandalism.

8Why is an exposed cable at lane 1 appeared at lane 2 down the road?

Underground cable may change its course during laying to suit site conditions or to avoid existing obstacles. Road realignment may also be carried out after the cable was laid, that could be the reason why we see the same cable appearing at the “other side” of the road.

9Why are pipes exposed instead of the cables that were indicated on the drawings?

There are two possible scenarios:

1. The indicated cable has not been exposed, it could be possibly laying in the pipe vicinity.

2. The pipes are carrying the power signal.

10After digging a few trial holes, it was noticed that there are 2 layers of utilities with approx. 1.5m apart, why?

The road level may be raised after the first set of utilities were laid. As a result, the second set of utilities though laid at standard depth may appear to be sitting on a separate layer. It is a good practice to dig trial holes starting from an old road surface so as to ensure site conditions as such can be observed.

11What shall I do if my work is very near the utility?

You should expose the complete length of the covered utility to clear your doubts on possible danger zone around them.

12If I need to jack a pipe under the utility, what shall I do?

You must make sure there is enough space clearance between the top of the tunneling / pipe jacking and the known utility.

13How to reduce the risk of damaging detected utilities?

You should engage an experienced Site Supervisor to supervise works that are near the detected utilities. Most incidents happen in the absence of site supervision.

14What shall I do if damage is done to the utilities?

You must inform the relevant Utility Provider immediately and carry out repair work accordingly. If any cable is damaged, you must also inform the relevant Cable Detector.