The motor switchboard, as shown in Figure below, provides the means for turning the pump motor on and off, and provides electrical protection for the motor and cable.
If we start at the line side of a switchboard and move through to the load side, we will find something similar to the Switchboard shown in the figure below.
This switch is used to disconnect the controller from the main power supply after the motor has been stopped.
ESP Power Cable Accessories, namely: Cable Bands and Cable Guards, are used to protect and support ESP cable, control lines and injection lines. There are used also to protect the power cable from damage during installation, operation and pulling. In this article, the roles and specifications of these accessory equipment’s are detailed, as well as recommended practices related to their use and selection.
Cable bands are used to attach the cable to the tubing during installation. Bands are provided using three different materials. Black Steel Bands are used in wells with corrosive problems. Stainless Steel Bands are used in moderately corrosive well (with no H2S present in the well). And Monel Bands are used in corrosive environments.
Most cable bands are 3/4 in. (19 mm) wide and approximately .025 in. (0.6 mm) thick.
Cable bands can be installed by using hand-banding tools or by using power-banding tools. The advantage of power banding tools is the bands are attached with the same tension.
The following video shows how to install Cable bands using Power-Banding Tool:
Recommended practices related to cable bands and their use:
The Motor Lead Extension is a “special power cable extending from the pothead on the motor to above the end of the pump where it connects with the power cable (API RP 11S4).
A low-profile cable (flat configuration) is usually needed in this area due to limited clearance between the pump housing and the well casing”.
It is recommended to select a length at least 6 ft. (1.8 m) longer than the upper end of the pump. The length of MLE has to be select in a way to avoid a splice over a tubing collar. Doing so could allow the cable to catch on the wellbore casing and damage the equipment.
The motor lead extension operates under extremely adverse conditions. This is due to the restricted size, the high mechanical stresses, and the high temperatures involved. Because of these effects, motor lead extensions are usually replaced every time a cable is reused.
Cable power losses or power drop are due to the conductor resistance heating that occurs when current flows. These cable losses are more often called KW losses or I²R losses. This is expressed by the following formula:
Where: Power losses in kW units, I is the current (in amps) and R (in ohms) is the average conductor resistance.
How to lower the resistance in the cable?
Power lost in a cable depends on the cable length, cable size and the current through the cable. Therefore, there are three ways to lower the resistance in the cable:
By Burney Waring, Consultant at WaringWorld, Inc.
One of my clients brought this diagram to my attention recently. The paper, by Petroleum Development Oman and Engineering Insight Ltd of Aberdeen, was very useful and included an especially useful diagram, but the diagram was not so easy to read or print in a larger size. I tried to improve the image so that it would be even more helpful. All credit goes to the authors and their paper IPTC 17413 2014, available on SPE’s OnePetro.
Here is the full size diagram:
