Benefits of dry Air Filling in Transformer?

Dry air must be used to ventilate the inside of the tank when it is opened for internal fitting. The air must have a dew point less than -40°C and sufficient airflow for the number of operators in the tank must be maintained.

Do never use nitrogen or other gases than air for ventilation

When opening the transformer tank, care must be taken to prevent moisture or dirt entering the transformer or moisture condensing in the transformer. If wet air enters the transformer, it may be cooled by the tank wall below its dew point and condensed, so it will reduce dielectric strength of the transformer

Dry air should be supplied through hand hole during working or inspection. Care especially must be taken not to drop tools or foreign substances. It is recommended that tools used in the tank be tied to worker with a cord. When the work in the tank is completed, the inside of the tank should be inspected. For inside cleaning, the dry, clean and lint-free cloths should be used.

what is the graphite coating & Why it is used for power cables ?

Graphite is generally used as a conductive coating to enable a sheath test in the field or on the drum, where the cable may not be in contact with an earth medium (eg in conduits, or direct laid in non conductive trenches, or maybe sitting in insulated cable racks in tunnels). It gives it a continuous potential for the sheath test so the whole of the sheath insulation can be tested for damage during installation

One point cable junction

Safety for temporary Electrical installations

Cable sheath bonding

Single-core underground power cables with two-points bonding induce currents in their metallic sheaths. The sheath induced currents are undesirable and generate power losses and reduce the cable ampacity.  The values of the sheath losses in some cases could be greater than conductor losses, depending on various factors. Such these factors are type of cable layouts, cable parameters, cable spacing, sheath resistance, phase rotation, conductor current and cable armoring

SHEATH BONDING ARRANGEMENTS

Cable trenches installations

Trench Construction:

• The cable trench may be precast (Preferred) or poured in place (Non Preferrred).
• Poured-in-place trench walls to be formed, do not cast against existing soil.
• Exposed edges to be finished with edging tool.
• No customer conductor, including bare ground/bonding conductors, is to be installed in the trench. 

Photos for some cable trenches installations 

7VK61 breaker management relay for Various Protection Applications

Protection functions

• Single and/or three-pole auto-reclosure
• Synchro-check with live/dead line/bus measurement

Breaker Failure Relays (Code 50BF)

Breaker Failure Relays are three-phase, solid state relays designed to provide protection and security for the power system against failure of the monitored breaker. Breaker failure relaying is the use of a current monitoring relay to determine whether or not current continues to flow into a faulted circuit some time after a circuit breaker has been instructed to interrupt the circuit. In the event that current continues to flow into the faulted circuit (after a defined period of time has elapsed sufficient for the breaker to have interrupted the current), then the circuit breaker is considered to have failed, and steps must be initiated to trip the next set of breakers up stream in the power system. The back up scheme must be designed to isolate both the faulted circuit and the failed breaker. Following are several reasons why a breaker fails to clear a fault:

Required Electrical & Mechanical tests for Substation Equipments (5)

Required Electrical & Mechanical tests for Substation Equipments (4)

Required Electrical & Mechanical tests for Substation Equipments (3)

Required Electrical & Mechanical tests for Substation Equipments(2)

Required Electrical & Mechanical tests for Substation Equipments (1)

Gas Insulated Swichgear ( GIS) - GENERAL EARTHING INFORMATION

Earthing and return current conductors

Earthing conductors

Earthing conductors interconnect the GIS enclosure at numerous points with the earthing net (multipoint earthing). Being a component of the earthing system they effectively help to avoid dangerous touch voltages during a short circuit, and to keep HF transient overvoltages on a sufficiently low level during normal service. To meet these requirements they shall have low impedances at 50/60 Hz as well as in the HF range.

Relay list for 13.8 KV swichgear

Following is sample of required relays for 13.8 KV SWGR

Impact recorders for transformers shipping

Impact Recorders continually monitor and report in real-time the shock, vibration and environmental conditions experienced by structures, facilities or equipment during transit, storage and operation. ShockLog impact recorders register the direction, amplitude, and duration of impact force. Optional sensors record changes in temperature, humidity, atmospheric pressure, tilt and roll. A GPS/ GPRS tracking module is available to pinpoint the location of mishandling or exposure to adverse conditions.  impact recorders are acute impact detection devices, which help to deter, monitor and minimize damage at each link of your supply chain

types of impact recorders:

1- electronic

2- analog

Below is Sample of inspection report for electronic impact recorder