Measurand’s SAA Surge Protection Device (SAASPD) is designed specifically to protect a ShapeArray (SAA) from electrical surges caused by proximal lightning strikes. As with any equipment, there is no protection possible if lightning strikes the cable or SAA directly. To be effective the SAASPD is to be inserted as an interruption in the ShapeArray cable near the ShapeArray and connected to a grounding rod or plate using #8 AWG (8.37 mm^2) copper wire.
Figure 1: An SAASPD
In the event that a surge destroys the SPD you will need to be able to locate it so that it can be accessed and replaced. The SAASPD works in conjunction with the SAA232 to provide protection for the ShapeArray and the cable. When the ShapeArray is installed within 15 m (50’) of a data acquisition system containing an SAA232 or SAA232-5, the SAASPD may not be required.
SAASPD is designed to be used with a ground plate or a ground rod. An SAASPD consists of the following major components.
- Terminal Blocks
- Ground Wire
- Copper Lug
Figure 2: The major components of an SAASPD
Step 1 - Strip the Wires
Insert the cable attached to the ShapeArray into the gland farthest from the copper lug. Make sure that the gland is loose around the cable. Strip approximately 25 mm of the insulation off the cable. Carefully cut away the white fabric followed by the clear plastic and foil around the twisted white and blue wires and the shielding wire. Strip the ends of the white, blue, red, and black wires.
Figure 3: ShapeArray cable with insulation and shielding stripped away
Note: The red wire shown in Figure 3 above is not stripped back far enough. This can cause a bad connection at the terminal block.
Step 2 - Wire the Terminal Blocks
Sand the cable behind the wires with the included sandpaper to allow the epoxy to properly adhere to the cable insulation. The sanded section should measure approximately 25 mm. Strip the insulation off each of the wires approximately 6 mm, as shown in Figure 3 above. Attach the wires to the 5-pin terminal block as shown in Figure 4 below.
Figure 4: Wires from the ShapeArray cable connected to the 5-pin terminal block
Pull the cable back and place the terminal pin block into the receptacle. Twist the set of wires to provide strain relief and connect the terminal block to the board. Ensure this is done for both sides
Step 3 - Tighten the Gland
Tighten the gland. Make sure that the blue insulation is tight inside the gland to avoid water intrusion and epoxy leaking. The black rubber gland will bulge approximately 1 mm when tightened. Ensure this is done for both sides.
Figure 5: Rubber gland prior to tightening
Step 4 - Test It
Test the ShapeArray before potting the unit. Hook the SAASPD up to your data acquisition system and your ShapeArray to ensure communication is working.
Figure 6: Connect the SAASPD to the data acquisition system and the ShapeArray and test communication prior to potting
Step 5 - Apply Potting Compound to the SAASPD Unit
Pot the SAASPD unit with the supplied 3M 2131 potting compound following the directions on the package and using the supplied gloves. In colder weather make sure to warm up the potting compound before mixing. Thoroughly mix the potting compound for 1 minute before using.
Figure 7: Mix potting compound and apply to assembled SAASPD unit
Step 6 - Complete Installation
Attach the cover to the SAASPD. Attach the ground wire to the copper lug on the back of the SAASPD and the ground rod. Mount the SAASPD in its final location using zip ties or other suitable means.
Figure 8: A completed SAASPD installation
The following three Figures provide detailed diagrams illustrating recommended applications for using an SAASPD for lightning protection.
Figure 9: A recommended configuration for SAASPD usage
Figure 10: Another recommended configuration for SAASPD usage
Figure 11: Another recommended configuration for SAASPD usage
The three Figures above are attached as files with detailed diagrams for applying an SAASPD to your installation for lightning protection.
- Diagram 1 - Lightning diversion system and protective ground system
- Diagram 2 - Lightning diversion system and protective ground system Optical Fiber or Radio Link
- Diagram 3 - Lightning diversion system and protective ground system local only