Underwater connector with electrical stress reduction

Details Underwater connector with electrical stress reduction Underwater connector with electrical stress reduction

2001-04-12

2003-12-09

Prasad, Chandrika (Department: 2839)

Electrical connectors

Including elastomeric or nonmetallic conductive portion

Inductive shielding or arc suppressing means

C439S271000

Reexamination Certificate

active

06659780

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a connector for making an electrical connection underwater or in a wet or conductive environment.
BACKGROUND OF THE INVENTION
An electrical connector capable of being mated and demated underwater is known from GB 2192316. This consists of a first connector part in the form of a plug and a second connector part in the form of a receptacle. To mate the connector, the plug is inserted into the receptacle. The plug houses a set of electrical socket contacts and the receptacle surrounds a corresponding set of electrical connecting pins which, when the connector is mated, engage in the sockets to establish electrical connections. The plug contains dielectric fluid for electrically isolating the various socket contacts from each other. The dielectric fluid is held in a flexible bladder which enables the pressure inside the bladder to balance with respect to external pressure and hence reduce any tendency for contaminants to enter the bladder. The plug, when demated, is sealed closed at the front by a set of shuttle pistons which pass through openings in a corresponding set of seals. When the plug is mated in the receptacle, each electrical connecting pin engages a respective shuttle piston and pushes it back against the force of a spring. The pin passes through the seal opening, in sealing engagement with the seal in place of the pushed back shuttle piston, and makes electrical contact with its corresponding socket contact.
The electrical connecting pins used in such connectors each have a metallic conductive core encapsulated by an insulating material, this insulating material forming the sealing surface of the connecting pin. Thus, when the connector parts are mated the pin insulation passes through and seals against a corresponding seal at the front of the plug. When the connector parts are fully mated the seal is stationary as an interference fit upon the pin insulation. To avoid hydraulic lock of the two connector parts, the receptacle is free flooding thus encompassing the pin contact insulation with ambient water, usually seawater. The seal is under compression, acting as a water tight barrier.
The design described above functions fine until the working voltage of the connector needs to be increased to a value where electrical stress becomes a major concern.
FIG. 1
shows an axial cross-section of a known connecting pin
1
of the type shown in GB 2192316. The pin
1
provided on a receptacle
3
passes through a seal
2
provided at the entrance to a plug connector part
4
containing dielectric fluid
5
. The pin
1
has a conductive core
6
encapsulated in insulation
7
which is exposed to ambient seawater
8
in the free flooded receptacle to the left of the seal
2
. The conductive core extends forwardly (to the right in the drawing) to where it has a contact portion (not shown), for making electrical contact with a socket contact (not shown) of the plug connector part. The distribution of voltage equipotentials within the insulating materials which are obtained with the connecting pin design of
FIG. 1
are shown in the Figure, at 12½% intervals. The equipotentials converge around the front seal
2
of the plug connector part
4
. This is due to the earthing effect of the seawater which free floods the receptacle void during connector deployment and mating. As the pin comes into contact with the seal, the equipotentials in the various insulating materials of the plug connector part converge into the pin insulation. This part of the assembly is the region where the highest electrical stresses exist, and is of concern at high voltage, for example voltages in excess of 14 kV. If the stress in this region reaches a level at which degradation of the insulation takes place, the connector will eventually fail.
Moreover, there is not only a high voltage gradient in the material of the seal, there is a high voltage gradient at the interengaging sealing surfaces of the seal and the pin The presence of a high voltage drop along a short distance could be high enough to initiate surface tracking along the interengaging surfaces of the seal and pin, and hence leakage of current to the surrounding water. This problem is amplified by the possible presence of water molecules at the interengaging surfaces, entering during mate/demate cycles. Thus, the inventors have recognised that the location of the converging voltage equipotentials in the material of the seal and the interengaging surfaces of the seal and the pin is problematic.
In addition to the difficulties caused by the location of the converging voltage distribution, the inventors have further recognised that due to the geometry of the assembly, the voltage distribution across the seal is condensed The water acts as an earth and effectively has a pointed profile, as viewed in a axial cross-section, at the interface
11
between the water, seal and pin. The condensed voltage distribution at this interface makes the above problems of potential seal degradation and surface tracking even more acute.
SUMMARY OF THE INVENTION
According to the invention, there is provided a connector for making an electrical connection underwater or in a wet or conductive environment, comprising first and second connector parts for engagement with each other to establish the electrical connection, the first connector part having a connecting pin provided with an insulating layer around a conductive core leading to a first electrical contact portion, the insulating layer being partially screened by a screening conductive layer, the second connector part having a second electrical contact portion for engagement by the first electrical contact portion, and the second connector part having a seal arranged so that in the mated condition of the connector the connecting pin extends forwardly through an opening in the seal, the first electrical contact portion then making contact with the second electrical contact portion, wherein when the connecting pin passes through the seal, the screening conductive layer is arranged to reduce electrical stress at the seal.
By providing the screening conductive layer around the insulating layer it is possible to avoid excessively high electrical stress in the seal and at the interengaging surfaces of the seal and the pin. The risk of the electrical stress in the seal reaching a level approaching the breakdown stress of the seal can be reduced and hence the likelihood of degradation of the seal leading to eventual failure can be reduced. Also, tracking along the interengaging surfaces of the seal and the pin may be avoided.
A reduction of the voltage gradient in the seal and at the interengaging seal and pin surfaces to an acceptable level may be obtained in some embodiments by appropriate design of the geometry of the conductive layer and the insulating layer in the vicinity of the water/seal/pin interface. For example, this geometry can be such as to guide the equipotential field lines evenly into the seal, with no localised condensing of field lines as shown at the interface
11
of FIG.
1
.
In such an arrangement, the conductive layer may extend forwardly from outside the seal to terminate, in the mated condition of the connector, at or adjacent the outside of the seal The conductive layer may terminate outwardly of the seal, but preferably the conductive layer is arranged so that in the mated condition of the connector it extends forwardly from outside the seal at least partly into the seal opening. By arranging the conductive layer to extend at least partly into the seal opening, the region where there is a voltage gradient is removed from the critical area at the water/seal/pin interface and is located instead inwardly of the interface.
It is particularly preferred for the conductive layer to be arranged so that in the mated condition of the connector it extends forwardly from outside the seal and into the second connector part, beyond the seal opening The voltage gradient is then even further removed from the water/seal/pin interface and indeed is advantageous

Affiliated with

Also associated with

Rating

Underwater connector with electrical stress reduction does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Underwater connector with electrical stress reduction, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Underwater connector with electrical stress reduction will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3111135