TEST OF THE OUTER PROTECTION OF THE BURRIED JOINT IN ACCORDANCE WITH IEC 60840

Fig-Typical Medium Voltage Cable Joint

Here in this article we will find a case study of type test report for direct buried type cable joint. Hope these text will help us to understand what kind of test actually required for underground power cable direct buried joints. In another article “TYPE TESTS ON COMPLETE UNDERGROUND POWER CABLE” we discussed detail a case study to make sense on type test of an XLPE cupper core underground power cable.

Dry heating cycle test in accordance with IEC 60840

On the joint three heating cycles without voltage were performed. Each heating cycle consisted of 8 h heating and 16 h of natural cooling. During the last 2 h of each heating period the conductor reached a temperature of at least  95 C (5 C above the maximum rated temperature).

Result: The test was performed in a correct way.

Water immersion and heat cycling in accordance with IEC 60840

After the three dry heating cycles, mentioned under 3.1 the joint was immersed in water, at a depth of at least 1 meter at the highest point of the outer protection. Then the joint was subjected to 20 heating cycles. In each heating cycle the water around the joint was heated to a temperature between 70 °C and 75 °C (between 15 °C and 20 °C below the maximum rated temperature of the cable conductor) and kept on this temperature for at least five hours. Hereafter the water was cooled down to a temperature less than the ambient temperature +10 °C.

Result: The water immersion and the heat cycling did not give reason for remarks.

DC voltage test on insulation joint in accordance with IEC 60840

After the water immersion and heat cycling, a voltage of 20 kV DC was applied for 1 minute between the metallic screen and the earthed exterior of the joint outer protection. Hereafter a voltage of 20 kV, DC was applied for 1 minute between the metallic screens on both sides of the joint. The test was carried out while the test installation was at ambient temperature.

Result: No breakdown occurred.

Impulse withstand voltage test on insulation between the screens and water in accordance with IEC 60840

Sponsored:

After the above mentioned tests the test set-up was tested with an impulse voltage of 37.5 kV. The test voltage was applied between the metallic screen and the earthed exterior of the joint outer protection. The test was carried out while the test installation was at ambient temperature.  The test was carried out in accordance with IEC 60230. The joint was tested with ten positive and ten negative voltage impulses.

Result: No breakdown occurred.

Impulse withstand voltage test on sheath sectionalizing insulation in accordance with IEC 60840

After the above mentioned tests the joint was taken out the water and the sheath sectionalizing insulation was tested with an impulse voltage of 75 kV. The test voltage was applied between the metallic screens on both sides of the joint. The test was carried out while the test installation was at ambient temperature.  The test was carried out in accordance with IEC 60230. The joint was tested with ten positive and ten negative voltage impulses.

Result: No breakdown occurred

Examination of the joint in accordance with IEC 60840

The joint was dismantled and inspected for water penetration and cracks.

Result: No signs of cracks or water penetration were detected. The construction of the joint complied with the construction drawing.

Hope this article on TEST OF THE OUTER PROTECTION OF THE BURRIED JOINT IN ACCORDANCE WITH IEC 60840 is helpful for you and your friends. If you think it’s need some add, put your comments below- comment space.

Extending Time Completion for an Underground Cable Transmission Line Project

Project Management

We wish to bring your kind attention that the contractual completion time under the subjected contract is five hundred forty (540) days from the effective date. But the progress of the work has been unduly delayed to the reasons beyond our control and not attributable to us, and would not be completed within the above mentioned time. Your kind consideration, we requested before for extending time completion in our memo no.-/Lot-2/07-11-13, dated on 18- November-2013 (copy enclosed).

There were confident events as specified herein which caused delayed us to complete the work within the contractual time.

The followings are the causes of delay in execution of the work under the contract:

01. Rampura – Madartek 132kV line route changed: 

Initially 132kV UG cable line route for Madartek substation was designed and approved from Maniknagar substation. As per approved design, we brought cable from Korea and took necessary step to execute the work. But just before start the cable pulling work, DPDC authority took decision to change route line from Rampura to Madartek substation which takes additional 4 month for new survey, design and getting approval. Due to change and new estimated 132kV Rampura-Madartek route line, the contract Time for Completion, Estimated Cost & Facilities are changed which is re-considerable as per GCC sub-clause 39.2.

02. Canal Crossing for Rampura 132KV line:  

There was no any canal crossing included in previous 132kV UG cable route line, but in changed Rampura to Madartek line there need to cross about 60m wide canal. It takes additional time to survey, design, estimate and getting approval. It is notable that canal crossing is possible only in dry season and 3 month obligatory additional time required particular for this job.

 03.  Madartek Substation is not ready:  

Madartek substation is not ready yet to cable pulling and termination. We paid DCC road cutting compensation for Rampura-Madartek line and started cable laying work as per schedule.   But due to substation not ready and getting better progress we did complete 5 span cable pulling within July 2013 and left 1st span from Madartek substation. Substation inside civil work, cable trench, termination point is not ready. Moreover inside substation cable route line is blocked with semi-paka building, lot of cable drum, heavy metallic garbage which not removed in time however we request several times.

Sponsored:

04. Rampura Substation Bay is not Ready: 

Bay extension at Rampura substation for 132kV cable termination is not completed yet. Bay extension and inside substation route line with entry into substation also need to locate for cable pulling.

05. Lalbagh OH tower & Substation is not ready: 

Termination tower for Lalbagh OH line and substation is not completed. Civil work, cable trench, termination point is not ready yet. Cable route line inside substation is not free for work, blocked with semi-paka building, existing contractor, metallic and wooden garbage which is requested to remove and free the area. We completed 33kV cable laying work in March 2013 for Lalbagh to Mitford link, but termination and energizing is pending due to substation is not ready.

06. Agargaon Substation is not ready: 

Sher e Banglanagar to Agargaon 33kV UG cable line laying and jointing work is almost completed, but Agargaon substation is not ready to cable termination and energizing.

07.  DCC & PWD road cutting obligation: 

There is seasonal obligation in DCC & PWD area for road cutting in rainy season from July to October. We got road cutting permission for Sher e Banglanagar to Agargaon and Rampura 132kV canal crossing for after rainy season.

08.  Unavoidable Circumstances: 

Carrying materials and moving working personnel to site during countrywide continuous hartal /strike is very much difficult and unsafe. Especially heavy cable drum, cable protecting slab, back-filling sand is need to carry from outside the city, truck and crane are not available during hartal time.

We expect that above the matter will cause the delay of completion the work by the contract time. Hereby, mentioned that we have paid obligatory and unavoidable 7 month for 132kV route line change & canal crossing work, otherwise all work was possible to complete before contractual time, because about 80% work completed within July 2013.

According to clauses GCC 39.2 & 40, we herewith submit to you a notice of claim for time extension for additional six (6) months for completion of contractual works without imposing any Liquidate Damage.

Difference Between Lightning and Surge Arrester

What is Lightning Arrester and What is Surge Arrester?

If you ask a question ''what is the difference between lightning arrester and surge arrester," answer will be vary  from man to man depending on his field of work or his experienced field. We can go some answer:

Lightning arrestor is to provide some degree of protection from Lightning induced problems. Surge arrestor is used to try to limit damaging surges, they can be against current surge, but more usually Voltage surges. . . Could be used on 5V supplies, 12V supplies, Mains 120V or other supply lines. . . Even used on Telephone lines. . . . It all depends on what you want to protect and from what ?

To know more about Lightning  Arrester and Surge Arrester you may visit full article on Surge Arrester Specification.

Sponsored:

Lightning Arrestors are located at highest elevations of the protected premises and are aimed to direct the discharged currents of lightning strikes through intended circuit to the ground (rather than for instance through the steel structures of a building). Surge Arrestors are voltage limiting devices that are installed on power electric circuits to limit the induced voltages (resulting from, say, switching devices, ground faults, etc.) on power apparatus (mainly) to protect the insulations within withstand levels.

The term "lightning arrester" is no longer used in power transmission. "Surge arrester" is the term used. This is the terminology adopted and followed by IEC. All over-voltages, be it due to lightning or switching or sudden load shedding, is taken care of by a "Surge arrester" in a substation. However, a new terminology, "Line arrester", is being used nowadays for arresters used in LV /MV transmission / distribution lines.

Whenever any inductive load is switched OFF, it induces voltage surges called switching surges into the system (following the equation E = L di/dt). These surges could be harmful to voltage sensitive devices connected in the system. As the contactor coil is inductive, switching of contactors could create switching surges that could harm other equipment. Also, external switching surges could harm the contactor coil itself. A surge suppressor connected to an LV contractor protects the contactor from external surges and also protects the system from being affected by the surges generated due to contractor switching.

Typical Routine Test for Metal Oxide Lightning Arrester

Following routine tests should be conducted and recorded the measured test result as per required standards on all the arresters fitted with accessories, here as example considered 198kV 10kA 3 part arrester, each 66kV and reference standard IEC 60099-4 of 2006& IS 3070 (Part 3) of 1993:

1. Measurement of power frequency reference voltage: All the arrester units should be tested for reference voltage at reference current of 3mA (crest). The reference voltages on each of arrester units must found greater than rated voltage of the arrester;
2. Measurement of Partial Discharge Voltage: All the arrester should subjected to test. The measured value should be less than the specified value (here specified value 10pC);
3. Measurement of Residual Voltage at Nominal Discharge Current: If possible, all arrester should be subjected to this test at nominal discharge current (here considered discharge current 10kA for 8/20 mic.sec wave). The measured value must be less than the maximum specified value (here specified value 650kVpeak);
4. Seal Leak Test: If possible, all arrester should be subjected to seal leak test by differential pressure/ bubble method. The units must be passed the test without any leakage;
5. Visual Examination and Dimensional Verification: All the arresters must visually examined and found free from any kind of visual defect. All dimensions should be within specified drawings, not exit tolerance limit;
6. Functional Test on Surge Monitor: I) Test on Milli Ammeter- The selected surge monitors should connected in series with arrester and the MCOV must be applied. The applied voltage and leakage current passing through the arrester must be recorded in milli ammeter. ii)- Test on Surge Counter on Standard Impulse Current: Surge monitor must be connected in series with the arrester and surge current pulse of 100A & 10kA (8/20mic.sec wave shape) should pass through the arrester for three times each current and the counter recorded each of the given impulse.

To know more about Insulator and Bushing mounting click full article on INSULATORS AND BUSHINGS MOUNTING.

Difference between Lightning Arrester and Surge Arrester

Yahoo selected the best answer by vote is as- This is mainly a matter of semantics. Historically, the motivation for using arresters was to deal with lightning, so they were called 'lightning arresters'. But as system voltage increased, it became apparent that there could be switching-induced surges that were more damaging than lightning, so today, the preferred term is probably 'surge arrester'.

There is a technical distinction between a 'surge suppressor' and a 'surge arrester' that has to do with the energy dissipation capability built into the device. The device that most people plug computers into is a 'surge suppressor' and has a fairly low energy dissipation capability. It also has a voltage rating that is only slightly greater than the normal system voltage. A typical 'surge arrester' has a far greater energy dissipation capability, and the voltage rating is driven more by the surge voltage withstand capability of the insulation being protected than by the rated system voltage.