I've never heard of a documented case of static electricity causing black powder to ignite.
Electricity's power is measured by two things which work hand in hand with each other.
The first is "voltage", which can be thought of as the power that causes the electricity to move thru something. The second is "amperage" which can be thought of as the real power or the thing that actually does the work. To find out how much work a charge of electricity will do we multiply the voltage times the amperage and come up with something called a Watt. Yes, it is the same "watt" that is shown on a light bulb or a microwave ovens tag.
Electricity also has another strange feature. It comes in positive (+) and negative (-) forms and if it is in the positive form, it doesn't like the other positive electricity around it. Likewise, if it is in its negative form, it doesn't like any other negative electricity.
Static electricity has a huge amount of voltage. That's why it can jump thru air creating a spark. It also has very little amperage so even if the spark hits something it doesn't create a lot of heat. (Yes, I know that lightning is static electricity and lightning can cause fires but the reason for this is, a lightning bolt has so much power like in the millions or billions of volts, that there is also enough amperage to cause enough heat to light something like a tree or your house on fire.)
Static electricity is also different from the spark in a spark plug in your car. The spark in your car has a lot of amperage in it so the spark from a ignition system does create a lot of heat as it travels from one spark plug electrode to the other one. The air and gasoline vapor between the electrodes creates the resistance needed to bring out the heat from a ignition systems spark.
In order for electricity to make heat, which is needed to cause black powder to light, we must have something that resists the flow of electricity thru it. If the electricity can pass thru something easily little or no heat will be made. (Think of a copper electric wire). If something does have a lot of resistance, if there is enough voltage to allow the electricity to pass thru it a lot of heat will be made, like the filament in a incandescent light bulb.
Black powder has a lot of carbon in it and carbon is a fairly good conductor of electricity so when the static charge hits some black powder it just travels around the outside of it (remember, it doesn't like itself so the charge on one side of a grain of powder pushes the charge on the other side away from it), and because of the low resistance, it doesn't create enough heat to light the powder.
No heat? No boom.
