Interlock 6517b

Could you please say how can we disable interlock programmatically? 

Hello,
Interlock is a safety feature designed to protect users from harmful levels of voltage. The amount of support I am able to offer in return is therefore limited.
All information regarding Interlock can be found in the 6517B manual. Reference pages 3-12 and on for more information.
Model 6517B Electrometer User's Manual | Tektronix
 

Ive meant is possible turn off Interlock?

Because the 1000V supply poses a shock hazard, it makes use of an interlock signal.
Ideally, you would have a physical barrier/test fixture with a door and door-switch.
When door open, the open switch prohibits the high voltage operation.
When door closed, the closed switch permits the high voltage operation.

Figure 26 in the Reference manual, pg 314, illustrates this simple open vs. closed connection to the interlock connector.

This is similar to how a microwave oven and the door state behaves.

There is no means to turn interlock off.